Depend on the skill type or the EQ he had on that time, some skill leave the user a portion of his/her health after doing it, or his/her eq negate instant death, either leaving a bit way for recovering...
It's a promotional piece for the novel most likely, recently/ this last year there have been a bunch of ok ish mangas that have been axed for that reason
I know, I know deep in the depths of my black and flabby little heart that the whole next chap is gonna be a damn flashback, with maybe 2 pages of "the hero" getting what he deserves, and all the rest being bullshit childhood drama.