私をセンターにすると誓いますか？•Watashi wo Center ni Suru to Chikaimasu ka?

Promise Me the Spotlight

"If you can really make me the Center...then we can get married." Meet Mizuki Natsuno, the least popular member of the nationally acclaimed idol group, Melty Strawberry. She has an eternal fan in Koichi Okuta, who is always pouring heart and soul into supporting her. Normally, a fan would never get to interact with their idol beyond the stage. But one thing led to another, and Koichi now finds himself living together with Mizuki in his own house. He vows to make her the new Center of Melty Strawberry, sparking an unconventional tag-team between a devoted fan and his idol. Together, they attempt to elevate Mizuki's career from obscurity to stardom! (Source: Kodansha)