Maiku Kamishiro is a high school photography enthusiast searching for his biological identity, having grown up as an orphan with no memory of his past. A pivotal clue leads him to a fateful encounter on a bridge in Lake Kizaki, where he meets two different girls, Karen Onodera and Maina Miyasumi, both claiming to be his twin sister based on identical childhood photographs and matching pendants. Seeking the truth, Maiku invites both young women to live with him in his lakeside apartment, sparking an emotionally charged and unconventional cohabitation dynamic.As the trio navigates daily life, romantic tension and deep
psychological complexities quickly overshadow sibling certainty. Maiku is driven by an intense desire for belonging and a fear of abandonment, while Karen and Maina harbor conflicting agendas and hidden feelings. Karen is outwardly bold, athletic, and fiercely protective, yet struggles with deep-seated insecurities about her place in Maiku's heart. Conversely, Maina is quiet, artistic, and emotionally fragile, masking a profound loneliness that draws her dangerously close to Maiku.The dramatic core of the narrative intensifies as local whispers, misunderstandings, and the claustrophobic nature of sharing a small living space push everyone to their emotional limits. Further complicating matters is their eccentric upperclassman, Tsubaki Minase, who harbors unrequited feelings for Maiku and frequently disrupts the household with her comedic yet poignant interventions. Secrets about their past begin to unravel through fragmented memories and old photographs, forcing the characters to confront uncomfortable truths about their lineage.As the narrative progresses, it is revealed through careful detective work and DNA verification that only one of the girls is Maiku’s true biological twin, while the other is linked to him through a deeply convoluted, tragic familial connection. This revelation shatters the fragile peace of their shared home, forcing all three to reevaluate their identities and emotional investments. Instead of driving them apart, the agonizing truth catalyzes
personal growth. Maiku stops running from his fear of isolation, embracing the complex web of chosen and biological bonds that define him. The series culminates in a bittersweet resolution where romantic boundaries are decisively drawn, unresolved grief is healed, and Maiku finally finds the stable emotional anchor and sense of family he has chased his entire life, forever bonded by the unforgettable summer spent alongside the pristine waters of Lake Kizaki.