Oh, Those Hanazono Twins volume 1

Tatara Tani is so average it hurts—the only thing he has going for him is that his childhood friends are ultra-popular idol Yuriko Hanazono and her fashionable twin, Rinko Hanazono! They're both his classmates, and his longstanding relationship with them makes others seethe. So he thinks he's hit the jackpot when Yuriko asks him to the amusement park with her, even though idols aren't allowed to date. She dresses up as Rinko to fool the world, but when her ruse is discovered by the school, it's up to Rinko to save her sister's reputation...by dating Tatara herself? This crazy rom-com of errors begins!