Nanno Koreshiki!

Toru Kurusu is the captain of the basketball club. However, he is the only member of the club, and the club is on the verge of being abolished despite his desperate efforts to recruit new members. One day, he finds a boy stuck head-first in the basket. The boy, who has extraordinary jumping ability, says he wants to join the basketball club...? (Source: Shonen Jump Plus, translated)