muu's invisibility and flight capabilities gives him an overwhelming advantage over minato and not only does it give him an advantage, but it gives him access to a wide variety of diverse tactics.
i'll elaborate on some examples.
1. muu can go invisible and set up traps over the vicinity surrounding minato. i.e. paper bomb traps, wire traps, ect. ect. and he can execute these traps in succession because minto cannot sense, or see him. and please dont use that lame excuse that minato can sense him on the ground because muu can fly which will make walking on the ground for him irrelevant.
2. muu can go invisible and and split his body in 2 and have his clone distract minato while muu sets up for an ambush. for example: muu's body splitting clone can distract minato with a jinton and minato will without a doubt teleport it away with his spacetime barrier but while he's doing that, muu can ambush him.
3. muu can use smoke bombs and cutt of minato's vision and hearing, due to the smoke noise the smoke bombs give off, and muu can kill minato that way.
im sorry but muu takes this with low to mid diffuclty. muu's attributes gives him acess to many diverse tactics that will utterly overwhelm minato with little effort. the circumstances are too much for minato to handle until kishi shows us more feats from him.
