Mewkledreamy: Ruka Kawada
https://mewkledreamy.com/
(Nice that the site cites "Theme Songs" and "Character Songs". Marvelous is publishing the OP/ED, wonder if they'll do these character songs too)
Yu☆Gi☆Oh: Sevens: Ryo Kawasaki
https://ja.wikipedia.org/wiki/遊☆戯☆王SEVENS
(For Yu-Gi-Oh on the other hand, with the change of all staff, wonder if Marvelous is still staying at music publishing)
Both Mewkledreamy and Yu-Gi-Oh SEVENS credit the music publishing to a company named MASTERHOOD, anyone ever heard about it?