Sonagi(2018)

Little Geuroo was curious about him. That boy from next door who asked him a strange question. The boy, Lee Garam, who always avoided him even though all Geuroo wanted was to get close to him. But before Geuroo could even confess, Garam disappeared in thin air, leaving only clusters of blue light behind. And then, one summer, he appeared in front of Geuroo as if nothing happened...?

(Source: Bomtoon, translated)

Note: Part of Kidari Entertainment's "Yeoreumdanpyeonseon: Some in Summer (~키다리이엔티 여름단편선~ 썸인썸머, Kidari Entertainment Summer Short Story Collection: Some in Summer)"