Mamahaha no tsurego ga moto-kano datta 2 (Kadokawa Sneaker Bunko) [Light Novel]

[Machine Translation] Mizuto and Yume, who became siblings after their parents remarried, are former lovers. They act like a "family" in front of their parents, but when they are alone, memories of those days come back to them, and they still care about each other. Then, Isana Higashigashira, a lonely otaku girl, appears in front of Mizuto, and the two hit it off immediately! The two hit it off right away, and spend after-school hours together in the library. Yume is annoyed by the distance between Mizuto and Isana, who claim with a straight face that they are just good friends, and that they are more than just friends. Moreover, Yume is also worried that Isana is getting closer to Mizuto than just a friend. ) Isana gradually realizes her love for Mizuto, and as "Mizuto's sister-in-law," she decides to support Isana. The "Mizuto strategy", where love, friendship, and sibling bonds are intertwined, is about to begin!

親の再婚できょうだいになった水斗と結女は、元恋人同士。両親の前では“家族”らしく振る舞うも、二人きりになるとあの頃の思い出が蘇り、やっぱりお互いが気になる日々で―。そんな中、水斗の前にぼっち系オタク少女・東頭いさなが現れ、二人はすぐに意気投合!図書室で放課後を過ごす関係に!?ただの気の合う友達だと真顔で言い張る水斗といさなの、友達以上な距離感に結女はやきもき。しかも、「わたし、水斗君の彼女に、なれますか...?」徐々に水斗への恋心を自覚していくいさなを、“水斗の義姉”として応援することに!?恋と友情ときょうだいの絆が錯綜する、『水斗攻略作戦』が始まる!