Kii

Kii is a Dryad who Papi rescues when she was taken by humans. Papi would then plant her in a forest near an illegal waste dump. However, Papi and Kii would become friends along with Suu later on. Because she was kidnapped by humans, Kii didn't like humans. Since Kii is a Dryad, she often absorbs the nutrients from the soil, but due to illegal dumping nearby, her body grew at an accelerated rate that would've become a problem if not dealt with. Luckily, you, Papi, and Suu manage to revert her to her original state. Kii appearance depends on how much nutrients she absorbs. Kii will appear in a more mature form if she absorbs enough nutrients form the soil to sustain it.