Onee-san Ha no Ore ga Naze Chicchai Kimi wo Suki ni Natta no ka?

It was spring break after middle school when Sky Toochika rescued a tiny girl in a packed train, as she barely even stood a chance against all those people. When he starts high school, the grade-schooler he thought she was turns up right here in his very classroom!? Her name is Chito Naruse: rather small, but drop-dead gorgeous—oh, and also a total energy addict. Then the little Chito-chan hits Toochika-kun straight up with a confession!? "I'm a devoted fan of tall, older onee-sans—so a cute, pint-sized girl like Chito-chan is not exactly my type. After turning her down, though, she just said that she'll twist my preferences outa shape… I'm kinda terrified!" Before long the two are spending time together as friends, and Toochika starts to see more than just the cute little girl in her…… A romantic comedy about an older-women-loving boy, a tiny girl, and their tug-of-war over preferences kicks off! (Source: KADOKAWA, translated)