It is probably a completely normal Ranchu
Look at the arched back, and the short, round tail
Although, it doesn't have the "normal" 90 degree angle tail tuck, but that's completely fine since he's not breeding or show stock
Here are a few pictures of the breeds so you can see the differences better!
Ranchu: Roundly arched back, small, round caudal lobes, 90 degree tail tuck.
Lionhead: Straight back, slightly bigger tail, much fluffier and larger headgrowth.
Lionchu: Pretty hard to spot the differences, they look very much like ranchus, but if you look at their tail and headgrowth, it's more like a lionhead