I don't get this
It's just a power plot. (You can't say a stronger demons name or it'll destroy you, whichever soul wavers is the weaker demon). Makoto has potential to make J's soul waver by making him fall in love w him & exploit his weakness (which was W).
He goes on a journey to get better, comes back, BOOM, he beats J and can now say his name. Jonathan (J) knows that M (makoto) loves him, so he calls out Ms name which consequently destroys him. Now M is lonely and trying to find a good candidate to repeat the cycle.
HAHAHAHA CRAULO KAYDEN BAT NAMAN KASE GANON YUNG LETTER NA BINIGAY NIYA KAY GUESTELLA GHAAHAHHA yan tuloy parang magkakaroon pa ng love interest dito