在夜之森小红16岁生日这天，妈妈送给她了一份特别的礼物——未婚夫。这个从乡下而来打算寄住在小红家的三峰白夜，其实是爷爷早就为她相中的人，就在她满脑袋混乱的时候，白夜的妹妹真白因不放心哥哥也住进的小红家，可是还没等小红适应这种生活，白夜和真白就又都转入了小红所在的班级……

真白不能接受红绪在家与学校完全不同的“双重性格”，因此时刻躲着她，但红绪常常却以此为乐。吃饭的时候，真白说到了以前的事情，可话刚到嘴边就被白夜打断，以前到底发生了什么？白夜为何要对小红有所隐瞒？晚上，好奇的小红努力回想儿时在爷爷家的记忆，却什么也没想起来，本想询问真白，但她却因为看了UFO类的节目受到惊吓而处于游离状态。

由于红绪的光环太过耀眼，小姑真白才一直忽略了小红的优点以及人气，当她意识到时便立刻找白夜让他增加危机意识，这时，红绪向真白发出邀请，让她去学生会室喝茶，放学后单独相处的小红和白夜去买食材，期间小红还特意买为白夜和真白买了碗，这让小姑真白很是兴奋。周末打理完家务的小红从姐姐那里得知了儿时白夜曾救过自己的事情……

得知被白夜所救之事后，小红便心事重重，更糟糕的是自己居然还发起高烧，而在此期间，白夜和真白只能将就红绪的黑暗料理。经过休养，小红恢复健康，可她却因为忘记了当时的状况而无法面对白夜，她的这种态度却让白夜产生误解，致使白夜以常人难以想象的速度逃到公园，幸亏小红一路跟随将误会化解，虽然此事阴差阳错的加深了二人的羁绊，可白夜和真白似乎还有什么事情隐瞒着小红。

得知三峰家会有亲人来访，十分在乎对方对自己印象的小红开始紧张地做好迎接准备。外出购物的小红在路上遇到了一个迷路的女子，小红为其带路走回一町目，而女子的目的地正是小红的家，原来她就是三峰家来访之人——白夜和真白的妈妈。妈妈无意中说出的话正是真白和白夜一直隐瞒的事情，原来他们……

情人节就要到来了，在小姑真白和桃内的提议下小红三人一起来到商场挑选礼物，结果真白却因为欲望购买了一堆怪物玩具。之后小红在小姑真白和桃内的建议下亲手自作了巧克力，可是情人节当天，小红却意外的有些紧张不知道如何将自己做的巧克力送给白夜。而白夜也因为没有收到小红的巧克力而失落，最终小红能够成功的送出自己做巧克力吗？

末续对总在红绪身边出现的小姑真白十分嫉妒不爽，就在末续因为不爽偷看小姑真白时，仁子出现在末续身后，并决定帮末续调查小姑真白。为了完成调查仁子假借采访小红顺便接近小姑真白。放学后想要去厕所的小姑真白碰到了监视自己的仁子，更是误将仁子和末续当成了幽灵与怪物。最终仁子能够成功调查出小姑真白的真相吗？

小红从小姑真白那里得知末续与真白是同族的事后，决定先对红绪隐瞒这一情况。另一方面，红绪因为小红的秘密而胡思乱想烦恼不已。之后末续约真白聊聊，结果水火不容的两人连走路也要比赛。意外看到末续与真白争执的红绪，却认为两人是因为争夺自己而争执，之后更是因为小红的话大受打击。而末续与真白又会发生什么事呢？

小红因为担心末续与真白，于是偷听末续与真白和白夜的谈话，在小红听到末续对白夜说“请和我结婚吧”这句话后，小红情绪十分低落。之后白夜在仁子面前否定两人婚约的事，更是令小红大受打击。另一方面，末续在对白夜告白失败后，从仁子那里得知白夜否认了与小红的交往，决定继续追求白夜的末续会有什么计划呢？而对于出现的竞争者小红又会怎样呢？

Benio seems to grow colder towards Hakuya, who seems a bit downhearted when Kobeni denies confessing. Meanwhile, Kobeni clears up the misunderstandings surrounding the engagement with Konoha, who attempts to stave off Niko's interest in Kobeni by giving her a plain article to write about. Later, Mashiro explains to Kobeni that Konoha's interest in marrying Hakuya was only because they are the same species, revealing that Kobeni is also similar to them due to having half of Hakuya's power. The next day, Kobeni decides to buy her and Hakuya matching handkerchieves, also buying some for Benio and Mashiro.

Hakuya is troubled over what gift he should get for Kobeni to make up for White Day. Meanwhile, Mashiro is almost spotted using her powers by Niko, who becomes determined to investigate the existence of a 'flying humanoid'. Later, Mashiro suggests that Kobeni and Hakuya go on a date, though Kobeni turns it into an outing with Mashiro. On the way home, Kobeni discovers Hakuya has a scar over his right eye, quickly coming to the conclusion that he got it from saving her. The next morning, after Hakuya and Mashiro receive another letter from their clan, Kobeni discovers they have disappeared, along with their belongings.

As Kobeni worries about Hakuya and Mashiro, the only clue she has being a text saying they had gone back to the mountains, Mayura encourages her to go to the mountains herself to learn the true story. Taking refuge from the snow, Kobeni is eventually found by Hakuya and Mashiro, who had only returned home to harvest some edible plants that only grow on their mountain. Kobeni comes down with another fever as a snowstorm picks up, with Hakuya heading off to look for help whilst Mashiro uses an opportunity to look for firewood. Delirious from her fever and worried about people leaving her, Kobeni heads off on her own in search for them, with Hakuya managing to save her from falling off a cliff. After Hakuya agrees to be more open with Kobeni, everyone returns home to their everyday lives.