Yuito's parents in New York concern about his returning back Japan alone to enter high school. So their boss arranges him to live his 4 sons; Ousuke, Kaisei, highschooler Hotaka & a lil child Sei-chan. From the color pages, we already can guess who's the Seme. (｡^‿^✿)
Tenjou no Shita ni Koi