Strange little game, but I can't figure out how to level monster skills, does anyone have any idea how to do that? It's not fusing the same character, it's not evolving, it's not meta morphing.....
It's told when you fo the tutorial and in the tips when loading :
Fuse with a unit having the same skill (basically with the same unit - evolved / unevolved version).
Some unit skill are only lv1 max.
But the sad thing is that it's not 100% chance of upgrading a skill lv per fusion. On the other hand, you can get a multi lv up in one fusion. It's like flower knight for that aspect.
Ah crap, that explains it, I must have failed when I tried to use the same unit with the same skill. Bleh, thank you Of course, now I have to click through all my units to find like skills... -..-.