Kanojo no ane wa 2-shū-me no kanojo

“I’ll be waiting in the future.” A promise like that… it’s just impossible.

​Shibukawa Ryuuichi’s life changes the moment he steps into the home of his girlfriend, Asada Miharu, and meets her twin sister, Sayuki. Unlike the earnest, innocent girl he’s dating, Sayuki carries an aura of sophisticated maturity—and she has a secret that defies logic.

​『Actually… I’m the “Miharu” from the future.』

​Sayuki explains the unthinkable: she is a version of Miharu who time-leaped, reincarnating as her own twin sister to repeat her life. In that first loop, she and Ryuuichi drifted apart until their relationship shattered. Now, she’s back with a mission.

​『We failed each other once. So, I want you to practice with me… that way, you won’t have to lose her this time.』

​Overwhelmed by her ability to predict every coming event with terrifying accuracy, Ryuuichi is forced into a secret, co-dependent pact. But Sayuki’s “guidance” is far from innocent. Armed with future knowledge of his deepest desires and every hidden preference, she uses her “pre-studied” love to launch a meticulous, seductive assault on his senses.

​Caught between his pure-hearted girlfriend and the sister who knows his soul better than he does himself, Ryuuichi find himself drowning in a temptation he can’t resist.