During a VESPER staff review of Mahoro's life and activities following her entry into civilian life, a letter from Mahoro is read to the assembled officers. In it, she describes taking part in a "summer vacation group research trip" to explore the notorious "nine mysteries" of Hiryu School 4. Seven of these are generally acknowledged to be no more than standard rumors typical of any school; the remaining two, however, have not been as easy to put to rest. Of course what Suguru, Kiyomi and Toshiya don't know is that all through, the three girls, minus Mahoro, are playing them, as part and parcel of their own "human response to stress" research project. But seek, and ye shall find: it does not take much to send them running frantically through the school to get away from "red-haired Ando", according to legend, a girl who fell to her death from the school roof years ago and has been haunting the halls at night ever since. Mahoro herself is in on the joke, though she plays along. The twist, however, comes when, after becoming separated from the group, she comes across the real Ando, a ghost or spirit trapped in the school until she can confess her love to a boy whose own spirit is trapped in another part of the building. Reunited by Mahoro, the two ghosts, now freed - and together - disappear, and the letter concludes.

太白星总部收到了一封麻幌寄来的信，信上记载着最近所发的生的一件事。为了完成暑假作业中的团体研究报告“检证绯立第四中学的九项怪事”，麻幌与阿优的同学们在晚上到学校进行幽灵探查，并决定先从第八项怪事“红发的安藤安藤同学”开始调查，传说夜晚爬学校楼梯时就会出现一个以前在校舍摔死的女学生的鬼魂，一行人对此传言本来抱持着怀疑的态度，没想到……

太白星總部收到了一封麻幌寄來的信，信上記載著最近所發的生的一件事。為了完成暑假作業中的團體研究報告“檢證緋立第四中學的九項怪事”，麻幌與阿優的同學們在晚上到學校進行幽靈探查，並決定先從第八項怪事“紅髮的安藤安藤同學”開始調查，傳説夜晚爬學校樓梯時就會出現一個以前在校舍摔死的女學生的鬼魂，一行人對此傳言本來抱持著懷疑的態度，沒想到……

先日浜辺で起こった騒動について報告がなされていたヴェスパー本部に、まほろさんからの手紙が届いた。「暑中お見舞い申し上げます」。その手紙によると、ある日まほろさんは優のクラスメイトたちと、夏休みのグループ研究“緋立市立第四中学校の九不思議を検証せよ！”をすべく、夜の学校で幽霊探索に行ったらしく…。

해수욕장에서 일어난 소동에 대한 보고가 이루어지고 있는 베스퍼 본부에 마호로로부터 한 통의 편지가 도착했다. 그 편지에 의하면, 어느 날 마호로는 스구루의 같은 반 아이들과 여름방학 그룹 연구 ‘히류우 제4중학교의 9대 불가사의를 밝혀라’라는 프로젝트에 참여하여 아무도 없는 밤학교에서 유령 탐색을 실시하던 중 8번째 불가사의인 ‘붉은 털의 안도씨’에 관해 조사를 개시하고 싶다는 내용이였는데…