What the fuck do these dudes even do?
Like most JP celebs they usually will just do a lot of appearances on things till they either gain a following or are given a regular weekly/daily thing to do for radio or television.
Earlier in the manga you see Maruyama star in a film, he's a model for product advertising, he's used as the spokesman/guest presenter for an event, he does tv interviews, ect. Yuma was introduced explaining that he does a lot of staring in paranormal themed variety shows.
Japanese media and it's production outside anime/manga is a very interesting, and occasionally depressing, topic which I always suggest people look into.