User blog comment:Koishi-Komeiji/Mitama Yakumo/@comment-31760473-20191006141014/@comment-24965192-20191006143544

Yes, a massive debuffing Caster. Also great to slot against any enemy, even Riders, since she is not weak to them.

She has more drawbacks than just bad NP gain. What she wants is to use her NP as much as possible, but then keeping her alive is tough. If you spam that NP, you'll take more and more damage over time, and using the 1st skill to heal herself means you lose out on damage that you could've given to your team.

Her kit is also packed with demerits. The defense down is certainly not good to have on anyone, especially since it's an unremovable debuff for 3 turns.

The stun is strong, but it's also limited to strictly Servants. The other two effects are mediocre. Flat HP cut on the enemy is nice (note that it's HP drain, not HP absorb; Mitama doesn't gain HP from this skill), but it's only great on lower HP mobs. The 100% Instant-Kill resistance is nice too, but it's useless on Servants, great on mobs, but then she doesn't have an Instant-Kill NP.

The NP is indeed good. But if you NP seal and skill seal an enemy, what it means is that you're forcing the enemy to use their normal hits, with each chance a possibly proccing of crits. Since she doesn't have crit down, and 20% healing received down is pretty mediocre, it's probably not a good idea to zone an enemy down this way. Especially not against an Assassin with high crit rate, and which Mitama does not resist at all. Curse OC is never great, and one would probably only use it to get the free damage up from the 1st skill, which, like I said, you have a choice of losing out on the damage if you heal Mitama.

I think Mitama isn't as great on the surface. She has great effects, yes, but comes in a tricky play style. I might daresay she's a support that needs a support, honestly.

I am aware Mitama is not that good in MagiReco itself. Though, "not good" in PvP is the word you're looking for, I believe. Mitama is great against PvE enemies who are magical girls as since is one of the best at locking them down.