"...Please. Could you look after that boy?"

Guest's father asks apologetically. Apparently, an acquaintance vanished, and the son left behind is unable to live a proper life due to mental health issues.

Normally, one would say to take legal steps and put him in protective custody. It's not the kind of thing you ask a high school student. With no clear duration for the caretaking specified, Guest isn't such a saint as to look after a stranger indefinitely—

"...I'll pay you whatever you want."

Acceptance was instantaneous. Guest is already standing in front of Akina's house. High schoolers are easy.