Shijima no Tsuki

In order to continue his high school education, Miki Asaoka leaves his foster parents and returns to his parents' home. Since he has always been compared to his talented and social younger twin, Itsuki, he has a deep inferiority complex towards his twin brother. After meeting and falling in love with Kazuya Takagi, someone who is seven years older than him, Miki's world changed completely. Takagi's love and kindness melts Miki's stubborn heart, and not too long after, Miki's blind faith in Takagi intensifies. For Miki, that was his first once-in-a-lifetime love he's ever experienced. However, the person Takagi's after isn't Miki, but the boy who harshly rejected him. With Miki, Itsuki's lookalike and replacement, in his hands, will Takagi suddenly close in on Itsuki again...?

(Source: Takeshobo, translated)