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.
Yeah i noticed the power thing. Kinda cool for a plot tbh. Kinda sad tho that the situation's will repeat over and over
It say that Wald's poison is so vicious, then do you know why J touch his hand in his bedroom cause Wald to extinguished?
I don't get this