Yankee Shota to Otaku Oneesan

Saeki Kazuko is an ordinary otaku who has a thing for "two-dimensional shota" but somehow, she is being bothered a lot by a neighbor's child, Aikawa Ryuou, an elementary school boy who looks like a yankee but is pure by heart. Even though he earnestly approaches Kazuko, he shows it with honest feelings and partly some violence.

(Source: MangaDex)