Darenimo Natsukanai Tobikyuu Tensai Youjo ga, Ore ni dake Amaetekuru Riyuu

In my class there was an eight-year-old girl. She was a genius child who skipped grades, and her appearance was adorable like a princess. However, she was very cold by nature and reluctant to get along with anyone. I thought the only person she could trust was her sister who was also in the same school as her... but one day, when I gave her a candy, she suddenly clung to me very strongly! This genius princess who turned out to be very lonely was being spoiled with just me. The love she showed knew no bounds, and she was trying to set me up with her sister who was famous for being the prettiest girl in school so that she could become my sister-in-law? This is a story about a little girl who is lonely because of her intelligence, and an ordinary young man who can be found anywhere.

(Source: SB Creative, translated)