In Japan, Ni No Kuni originally released as two separate games, Ni No Kuni: Wrath of the White Witch for PlayStation 3 -- which later released worldwide -- and Ni No Kuni: Dominion of the Dark Djinn which released a year prior for the Nintendo DS.
In Ni No Kuni, you play as a boy named Oliver whose mother has just passed. After bringing a fairy plush toy to life through his tears, he sets out to find his mother in a fantastical alternate dimension, while also fighting against a great evil power. Oliver ventures through the magical world with some new friends and has the ability to obtain different Pokémon like familiars along the way.
With Level 5's other monster-taming RPG, Yo-Kai Watch, losing popularity, bringing their critically acclaimed RPG to a portable system may be a wise decision. They could maybe even add some familiars and other features exclusive to the Nintendo Switch version.