Pretty sure it's strap-on. It's even seen behind the blur. Sakimichan doesn't draw dickgirls unless it's canonic. As far as I know Power from Chainsaw Man is not futa.I think its futa (easier to draw) + next semester we will see an animation of this
Tbh I don't even remember any canonic futanari characters in non-hentai anime/videogames except replicant Kainé (intersex) from NieR and Poison (transgender) from Street Fighter.