Kobeni receives an unexpected 16th birthday gift in the form of an arranged marriage, a pact orchestrated by her late grandfather. Despite having supposedly met her betrothed, Hakuya, in the past, Kobeni retains no recollection of him. The arrival of Hakuya and his peculiar sister, Mashiro, at her home, joined by Kobeni's unsurprised mother and overly attentive sister, Benio, sets the stage for a bizarre cohabitation. As Kobeni and her enigmatic future family navigate daily life together, attending school unveils a myriad of oddities. From Mashiro's fixation on extraterrestrials and mysterious creatures to Hakuya's aloof demeanor, Kobeni detects an unsettling aura surrounding them. Intrigued by the mysteries shrouding her arranged marriage and the peculiar gaps in her memory, Kobeni delves into the enigma her grandfather has intertwined her life with.