diff --git a/server/prisma/migrations/20250401154435_add_course_cascade/migration.sql b/server/prisma/migrations/20250401154435_add_course_cascade/migration.sql
new file mode 100644
index 00000000..0de34369
--- /dev/null
+++ b/server/prisma/migrations/20250401154435_add_course_cascade/migration.sql
@@ -0,0 +1,14 @@
+-- DropForeignKey
+ALTER TABLE "Enrollment" DROP CONSTRAINT "Enrollment_courseId_fkey";
+
+-- DropForeignKey
+ALTER TABLE "Slot" DROP CONSTRAINT "Slot_courseId_fkey";
+
+-- AlterTable
+ALTER TABLE "Message" ALTER COLUMN "isPicture" DROP DEFAULT;
+
+-- AddForeignKey
+ALTER TABLE "Slot" ADD CONSTRAINT "Slot_courseId_fkey" FOREIGN KEY ("courseId") REFERENCES "Course"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "Enrollment" ADD CONSTRAINT "Enrollment_courseId_fkey" FOREIGN KEY ("courseId") REFERENCES "Course"("id") ON DELETE CASCADE ON UPDATE CASCADE;
diff --git a/server/prisma/schema.prisma b/server/prisma/schema.prisma
index 8f6bb750..4ebc225a 100644
--- a/server/prisma/schema.prisma
+++ b/server/prisma/schema.prisma
@@ -92,7 +92,7 @@ model Course {
 // コマ。1つの講義に対して複数存在しうる。
 model Slot {
   id       Int    @id @default(autoincrement())
-  course   Course @relation(fields: [courseId], references: [id])
+  course   Course @relation(fields: [courseId], references: [id], onDelete: Cascade)
   courseId String
   period   Int // 1-6. 0 の場合はなし (集中など)
   day      Day // 曜日。other の場合は集中など
@@ -104,7 +104,7 @@ model Enrollment {
   id       Int    @id @default(autoincrement())
   user     User   @relation(fields: [userId], references: [id], onDelete: Cascade)
   userId   Int
-  course   Course @relation(fields: [courseId], references: [id])
+  course   Course @relation(fields: [courseId], references: [id], onDelete: Cascade)
   courseId String
 
   @@unique([userId, courseId])
diff --git a/server/src/.gitignore b/server/src/.gitignore
index 3bfac405..f839c428 100644
--- a/server/src/.gitignore
+++ b/server/src/.gitignore
@@ -1,2 +1,3 @@
 /common
 /seeds/data.json
+/seeds/json
diff --git a/server/src/seeds/insertCoursesFromJSONByCreateMany.ts b/server/src/seeds/insertCoursesFromJSONByCreateMany.ts
new file mode 100644
index 00000000..98cf3451
--- /dev/null
+++ b/server/src/seeds/insertCoursesFromJSONByCreateMany.ts
@@ -0,0 +1,83 @@
+import * as fs from "node:fs";
+import * as path from "node:path";
+
+import { prisma } from "../database/client";
+
+// シ楽バス形式のデータを読み込む。
+const FILE_PATH = path.join(__dirname, "data.json");
+
+async function main() {
+  const jsonData = JSON.parse(fs.readFileSync(FILE_PATH, "utf-8"));
+
+  const coursesData = jsonData.map(
+    (course: {
+      code: string;
+      titleJp: string;
+      lecturerJp: string;
+    }) => {
+      const { code, titleJp, lecturerJp } = course;
+      return {
+        id: code,
+        name: titleJp,
+        teacher: lecturerJp,
+      };
+    },
+  );
+
+  await prisma.course.createMany({
+    data: coursesData,
+  });
+
+  const slotsData: {
+    day: "mon" | "tue" | "wed" | "thu" | "fri" | "sat" | "sun" | "other";
+    period: number;
+    courseId: string;
+  }[] = [];
+
+  for (const courseData of jsonData) {
+    const { code, periods } = courseData;
+
+    for (const period of periods) {
+      const [dayJp, periodStr] = period.split("");
+      const day =
+        dayJp === "月"
+          ? "mon"
+          : dayJp === "火"
+            ? "tue"
+            : dayJp === "水"
+              ? "wed"
+              : dayJp === "木"
+                ? "thu"
+                : dayJp === "金"
+                  ? "fri"
+                  : dayJp === "土"
+                    ? "sat"
+                    : dayJp === "日"
+                      ? "sun"
+                      : "other";
+
+      slotsData.push({
+        day,
+        period: Number.parseInt(periodStr) || 0,
+        courseId: code,
+      });
+    }
+  }
+
+  await prisma.slot.createMany({
+    data: slotsData,
+    skipDuplicates: true,
+  });
+
+  console.log("Data inserted successfully!");
+}
+
+main()
+  .then(async () => {
+    await prisma.$disconnect();
+  })
+  .catch(async (e) => {
+    console.error(e);
+    await prisma.$disconnect();
+    process.exit(1);
+  });
diff --git a/web/components/course/components/SelectCourseDialog.tsx b/web/components/course/components/SelectCourseDialog.tsx
index eafd7fbc..52f5dafa 100644
--- a/web/components/course/components/SelectCourseDialog.tsx
+++ b/web/components/course/components/SelectCourseDialog.tsx
@@ -20,6 +20,7 @@ export default function SelectCourseDialog({
   handleCoursesUpdate: (courses: Course[]) => void;
 }) {
   const [availableCourses, setAvailableCourses] = useState<Course[]>([]);
+  const [searchText, setSearchText] = useState("");
   const [filteredAvailableCourses, setFilteredAvailableCourses] = useState<
     Course[]
   >([]);
@@ -48,7 +49,14 @@ export default function SelectCourseDialog({
       onClick={(e) => e.stopPropagation()}
     >
       <form className="modal-backdrop">
-        <button type="button" onClick={onClose}>
+        <button
+          type="button"
+          onClick={() => {
+            setSearchText("");
+            setFilteredAvailableCourses(availableCourses);
+            onClose();
+          }}
+        >
           閉じる
         </button>
       </form>
@@ -64,7 +72,11 @@ export default function SelectCourseDialog({
         <button
           type="button"
           className="btn btn-ghost btn-sm absolute top-3 right-3"
-          onClick={onClose}
+          onClick={() => {
+            setSearchText("");
+            setFilteredAvailableCourses(availableCourses);
+            onClose();
+          }}
         >
           閉じる
         </button>
@@ -102,9 +114,12 @@ export default function SelectCourseDialog({
             type="text"
             placeholder="授業名で検索"
             className="input input-bordered mt-4 w-full"
+            value={searchText}
             onChange={(e) => {
+              const text = e.target.value.trim();
+              setSearchText(text);
               const newFilteredCourses = availableCourses.filter((course) =>
-                course.name.includes(e.target.value.trim()),
+                course.name.includes(text),
               );
               setFilteredAvailableCourses(newFilteredCourses);
             }}
@@ -140,6 +155,8 @@ export default function SelectCourseDialog({
             onClose={() => {
               setConfirmDialogStatus("closed");
               setNewCourse(null);
+              setSearchText("");
+              setFilteredAvailableCourses(availableCourses);
               onClose();
             }}
             onCancel={() => {