diff --git a/SVSim.EmulatedEntrypoint/Controllers/CampaignController.cs b/SVSim.EmulatedEntrypoint/Controllers/CampaignController.cs
new file mode 100644
index 0000000..bd19353
--- /dev/null
+++ b/SVSim.EmulatedEntrypoint/Controllers/CampaignController.cs
@@ -0,0 +1,93 @@
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using SVSim.Database;
+using SVSim.Database.Enums;
+using SVSim.Database.Models;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Campaign;
+
+namespace SVSim.EmulatedEntrypoint.Controllers;
+
+/// <summary>
+/// /campaign/* — promotional surfaces. Currently just <c>regist_serial_code</c>.
+/// </summary>
+[Route("campaign")]
+public sealed class CampaignController : SVSimController
+{
+    private const int FailureResultCode = 4202;
+
+    private readonly SVSimDbContext _db;
+
+    public CampaignController(SVSimDbContext db) => _db = db;
+
+    [HttpPost("regist_serial_code")]
+    public async Task<IActionResult> RegisterSerialCode(
+        [FromBody] RegisterSerialCodeRequest request,
+        CancellationToken ct)
+    {
+        if (!TryGetViewerId(out var viewerId)) return Unauthorized();
+
+        var now = DateTime.UtcNow;
+
+        var code = await _db.SerialCodes
+            .Include(c => c.Rewards)
+            .FirstOrDefaultAsync(c => c.Code == request.SerialCode, ct);
+
+        if (code is null) return Fail();
+        if (!code.IsEnabled) return Fail();
+        if (code.StartAt is { } start && start > now) return Fail();
+        if (code.EndAt is { } end && end < now) return Fail();
+
+        bool alreadyRedeemed = await _db.ViewerSerialCodeRedemptions
+            .AnyAsync(r => r.ViewerId == viewerId && r.SerialCodeId == code.Id, ct);
+        if (alreadyRedeemed) return Fail();
+
+        if (code.Rewards.Any(r => !IsSupportedGiftRewardType(r.RewardType))) return Fail();
+
+        try
+        {
+            _db.ViewerSerialCodeRedemptions.Add(new ViewerSerialCodeRedemption
+            {
+                ViewerId = viewerId,
+                SerialCodeId = code.Id,
+                RedeemedAt = now,
+            });
+
+            foreach (var reward in code.Rewards.OrderBy(r => r.Slot))
+            {
+                _db.ViewerPresents.Add(new ViewerPresent
+                {
+                    ViewerId = viewerId,
+                    PresentId = Guid.NewGuid().ToString("N").Substring(0, 16),
+                    Status = PresentStatus.Unclaimed,
+                    RewardType = reward.RewardType,
+                    RewardDetailId = reward.RewardDetailId,
+                    RewardCount = reward.RewardCount,
+                    Message = code.Message,
+                    CreatedAt = now,
+                    Source = $"serial_code:{code.Id}",
+                });
+            }
+
+            await _db.SaveChangesAsync(ct);
+        }
+        catch (DbUpdateException)
+        {
+            // Race: two concurrent redeems for the same (viewer, code). The composite PK
+            // on ViewerSerialCodeRedemption rejects the second one; treat as already-redeemed.
+            return Fail();
+        }
+
+        return Ok(new RegisterSerialCodeResponse { IsComplete = true });
+    }
+
+    private IActionResult Fail() => Ok(new { result_code = FailureResultCode });
+
+    /// <summary>
+    /// Gift wire types per <c>GiftController.WireRewardTypeToUserGoodsType</c>:
+    /// 1=Crystal, 4=Item, 9=Rupy. Codes with unsupported types fail-fast at redemption.
+    /// Note: wire "1" means Crystal (not RedEther), following the gift wire convention
+    /// rather than the <see cref="UserGoodsType"/> enum order.
+    /// </summary>
+    private static bool IsSupportedGiftRewardType(int rewardType) =>
+        rewardType is 1 or 4 or 9;
+}
diff --git a/SVSim.EmulatedEntrypoint/Models/Dtos/Campaign/RegisterSerialCodeRequest.cs b/SVSim.EmulatedEntrypoint/Models/Dtos/Campaign/RegisterSerialCodeRequest.cs
new file mode 100644
index 0000000..3ef5abb
--- /dev/null
+++ b/SVSim.EmulatedEntrypoint/Models/Dtos/Campaign/RegisterSerialCodeRequest.cs
@@ -0,0 +1,17 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Campaign;
+
+/// <summary>
+/// Body of <c>POST /campaign/regist_serial_code</c>. Client task:
+/// <c>MyPageCodeInputTask</c> (Shadowverse_Code_2026-05-23/Wizard/MyPageCodeInputTask.cs).
+/// </summary>
+[MessagePackObject]
+public sealed class RegisterSerialCodeRequest
+{
+    /// <summary>User-typed serial code. Case-sensitive on the server.</summary>
+    [JsonPropertyName("serial_code")]
+    [Key("serial_code")]
+    public string SerialCode { get; set; } = string.Empty;
+}
diff --git a/SVSim.EmulatedEntrypoint/Models/Dtos/Campaign/RegisterSerialCodeResponse.cs b/SVSim.EmulatedEntrypoint/Models/Dtos/Campaign/RegisterSerialCodeResponse.cs
new file mode 100644
index 0000000..3c57ba0
--- /dev/null
+++ b/SVSim.EmulatedEntrypoint/Models/Dtos/Campaign/RegisterSerialCodeResponse.cs
@@ -0,0 +1,16 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Campaign;
+
+/// <summary>
+/// Success response shape. Failure path uses an anonymous <c>{ result_code = 4202 }</c>
+/// (mirroring AchievementController/MissionController) and bypasses this DTO.
+/// </summary>
+[MessagePackObject]
+public sealed class RegisterSerialCodeResponse
+{
+    [JsonPropertyName("is_complete")]
+    [Key("is_complete")]
+    public bool IsComplete { get; set; }
+}
diff --git a/SVSim.UnitTests/Controllers/CampaignControllerTests.cs b/SVSim.UnitTests/Controllers/CampaignControllerTests.cs
new file mode 100644
index 0000000..3d2cbf0
--- /dev/null
+++ b/SVSim.UnitTests/Controllers/CampaignControllerTests.cs
@@ -0,0 +1,230 @@
+using System.Net;
+using System.Net.Http.Json;
+using System.Text;
+using System.Text.Json;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using SVSim.Database;
+using SVSim.Database.Models;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Controllers;
+
+public class CampaignControllerTests
+{
+    private static StringContent JsonBody(string json) => new(json, Encoding.UTF8, "application/json");
+
+    private static async Task<SerialCodeEntry> SeedCodeAsync(
+        SVSimTestFactory factory, string code, string message = "test message",
+        bool enabled = true, DateTime? startAt = null, DateTime? endAt = null,
+        params (int Type, long DetailId, int Count)[] rewards)
+    {
+        using var scope = factory.Services.CreateScope();
+        var ctx = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var entity = new SerialCodeEntry
+        {
+            Code = code,
+            Message = message,
+            IsEnabled = enabled,
+            StartAt = startAt,
+            EndAt = endAt,
+        };
+        for (int i = 0; i < rewards.Length; i++)
+        {
+            entity.Rewards.Add(new SerialCodeRewardEntry
+            {
+                Slot = i,
+                RewardType = rewards[i].Type,
+                RewardDetailId = rewards[i].DetailId,
+                RewardCount = rewards[i].Count,
+            });
+        }
+        ctx.SerialCodes.Add(entity);
+        await ctx.SaveChangesAsync();
+        return entity;
+    }
+
+    [Test]
+    public async Task Register_with_valid_unredeemed_code_returns_success_and_creates_presents()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+        var code = await SeedCodeAsync(factory, "VALID1", "Welcome reward",
+            rewards: new[] { (1, 0L, 100), (9, 0L, 500) });
+
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+        var response = await client.PostAsync("/campaign/regist_serial_code",
+            JsonBody("""{"serial_code":"VALID1"}"""));
+        var raw = await response.Content.ReadAsStringAsync();
+        Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.OK), raw);
+
+        using var doc = JsonDocument.Parse(raw);
+        Assert.That(doc.RootElement.GetProperty("is_complete").GetBoolean(), Is.True);
+
+        using var verifyScope = factory.Services.CreateScope();
+        var ctx = verifyScope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var presents = await ctx.ViewerPresents.AsNoTracking()
+            .Where(p => p.ViewerId == viewerId).OrderBy(p => p.RewardType).ToListAsync();
+        Assert.That(presents, Has.Count.EqualTo(2));
+        Assert.That(presents.All(p => p.Message == "Welcome reward"), Is.True);
+        Assert.That(presents.All(p => p.Source == $"serial_code:{code.Id}"), Is.True);
+        Assert.That(presents.All(p => p.Status == PresentStatus.Unclaimed), Is.True);
+
+        var redemptions = await ctx.ViewerSerialCodeRedemptions.AsNoTracking()
+            .Where(r => r.ViewerId == viewerId && r.SerialCodeId == code.Id).ToListAsync();
+        Assert.That(redemptions, Has.Count.EqualTo(1));
+    }
+
+    [Test]
+    public async Task Register_with_unknown_code_returns_4202()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var response = await client.PostAsync("/campaign/regist_serial_code",
+            JsonBody("""{"serial_code":"NOSUCHCODE"}"""));
+        var raw = await response.Content.ReadAsStringAsync();
+        Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.OK), raw);
+
+        using var doc = JsonDocument.Parse(raw);
+        Assert.That(doc.RootElement.GetProperty("result_code").GetInt32(), Is.EqualTo(4202));
+    }
+
+    [Test]
+    public async Task Register_with_disabled_code_returns_4202()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+        await SeedCodeAsync(factory, "DISABLED", enabled: false,
+            rewards: new[] { (1, 0L, 100) });
+
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+        var response = await client.PostAsync("/campaign/regist_serial_code",
+            JsonBody("""{"serial_code":"DISABLED"}"""));
+        var raw = await response.Content.ReadAsStringAsync();
+        using var doc = JsonDocument.Parse(raw);
+        Assert.That(doc.RootElement.GetProperty("result_code").GetInt32(), Is.EqualTo(4202));
+    }
+
+    [Test]
+    public async Task Register_with_pre_start_code_returns_4202()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+        await SeedCodeAsync(factory, "FUTURE",
+            startAt: DateTime.UtcNow.AddDays(1),
+            rewards: new[] { (1, 0L, 100) });
+
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+        var response = await client.PostAsync("/campaign/regist_serial_code",
+            JsonBody("""{"serial_code":"FUTURE"}"""));
+        var raw = await response.Content.ReadAsStringAsync();
+        using var doc = JsonDocument.Parse(raw);
+        Assert.That(doc.RootElement.GetProperty("result_code").GetInt32(), Is.EqualTo(4202));
+    }
+
+    [Test]
+    public async Task Register_with_expired_code_returns_4202()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+        await SeedCodeAsync(factory, "EXPIRED",
+            endAt: DateTime.UtcNow.AddDays(-1),
+            rewards: new[] { (1, 0L, 100) });
+
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+        var response = await client.PostAsync("/campaign/regist_serial_code",
+            JsonBody("""{"serial_code":"EXPIRED"}"""));
+        var raw = await response.Content.ReadAsStringAsync();
+        using var doc = JsonDocument.Parse(raw);
+        Assert.That(doc.RootElement.GetProperty("result_code").GetInt32(), Is.EqualTo(4202));
+    }
+
+    [Test]
+    public async Task Register_with_already_redeemed_code_returns_4202()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+        var code = await SeedCodeAsync(factory, "ONCE",
+            rewards: new[] { (1, 0L, 100) });
+
+        // Pre-seed a redemption record.
+        using (var seedScope = factory.Services.CreateScope())
+        {
+            var ctx = seedScope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+            ctx.ViewerSerialCodeRedemptions.Add(new ViewerSerialCodeRedemption
+            {
+                ViewerId = viewerId,
+                SerialCodeId = code.Id,
+                RedeemedAt = DateTime.UtcNow.AddMinutes(-5),
+            });
+            await ctx.SaveChangesAsync();
+        }
+
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+        var response = await client.PostAsync("/campaign/regist_serial_code",
+            JsonBody("""{"serial_code":"ONCE"}"""));
+        var raw = await response.Content.ReadAsStringAsync();
+        using var doc = JsonDocument.Parse(raw);
+        Assert.That(doc.RootElement.GetProperty("result_code").GetInt32(), Is.EqualTo(4202));
+
+        // Sanity: no new presents created.
+        using var verifyScope = factory.Services.CreateScope();
+        var ctx2 = verifyScope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var presents = await ctx2.ViewerPresents.AsNoTracking()
+            .Where(p => p.ViewerId == viewerId).CountAsync();
+        Assert.That(presents, Is.EqualTo(0));
+    }
+
+    [Test]
+    public async Task Register_with_unsupported_reward_type_returns_4202_and_no_redemption_row()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+        // RewardType 5 = Card; gift mapper supports only 1=Crystal, 4=Item, 9=Rupy.
+        var code = await SeedCodeAsync(factory, "BADTYPE",
+            rewards: new[] { (5, 100L, 1) });
+
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+        var response = await client.PostAsync("/campaign/regist_serial_code",
+            JsonBody("""{"serial_code":"BADTYPE"}"""));
+        var raw = await response.Content.ReadAsStringAsync();
+        using var doc = JsonDocument.Parse(raw);
+        Assert.That(doc.RootElement.GetProperty("result_code").GetInt32(), Is.EqualTo(4202));
+
+        // Critical: no redemption row created → admin can fix and player can retry.
+        using var verifyScope = factory.Services.CreateScope();
+        var ctx = verifyScope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var redemptions = await ctx.ViewerSerialCodeRedemptions.AsNoTracking()
+            .Where(r => r.ViewerId == viewerId && r.SerialCodeId == code.Id).CountAsync();
+        Assert.That(redemptions, Is.EqualTo(0));
+    }
+
+    [Test]
+    public async Task Register_without_auth_returns_401()
+    {
+        using var factory = new SVSimTestFactory();
+        var client = factory.CreateClient();  // no X-Test-Viewer-Id header
+
+        var response = await client.PostAsync("/campaign/regist_serial_code",
+            JsonBody("""{"serial_code":"WHATEVER"}"""));
+        Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.Unauthorized));
+    }
+
+    [Test]
+    public async Task Register_is_case_sensitive_for_code_match()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+        await SeedCodeAsync(factory, "MixedCase",
+            rewards: new[] { (1, 0L, 100) });
+
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+        var response = await client.PostAsync("/campaign/regist_serial_code",
+            JsonBody("""{"serial_code":"mixedcase"}"""));
+        var raw = await response.Content.ReadAsStringAsync();
+        using var doc = JsonDocument.Parse(raw);
+        Assert.That(doc.RootElement.GetProperty("result_code").GetInt32(), Is.EqualTo(4202));
+    }
+}