Seija's move is a Roar clone, so puppets with Iron Resolve (Kurumi and Elly are nearby and both get it) can block it. Koakuma however uses Changeling, which causes her to escape; you'll want something with Dark-absorption (Dark Clothing Defense Rumia and Negative Aura Murasa forms are the easiest to get) to stop it from working. If you're not nuzlocking though, both puppets are fairly common in the areas they appear so you're probably best off just throwing a seal turn 1 and one-shotting it on turn 2.
