Megвђ™s Monster Switch Nsp [update] (eshop) -

Players control a nearly invincible monster named Roy who must protect a young human girl named Meg in a world of monsters.

While Roy has 99,999 HP, the real challenge is keeping Meg happy. If Roy takes damage, Meg gets upset; if she starts crying, her power triggers the apocalypse, resulting in a game over. Meg’s Monster Switch NSP [Update] (eShop)

The specific phrasing in your query is common on gaming news and download sites: Players control a nearly invincible monster named Roy

Battles function as resource management puzzles where players use toys to maintain Meg's mental state while defeating enemies. Technical Terms Explained Meg gets upset