No type advantage (Litten)

(Even though I will assume that in the game, you are going to use its weaknesses, which is Ground, I need different paths to accommodate all three starters, so I'm going to go based on how your starter fares against the opposing Pokemon)

(If you were curious as to what I did, I just simply used Alolan Diglett against this mouse and it couldn't touch me.)

Pokemon Trainer Hau sends out Rowlet (level 14, Grass/Flying type)
Strengths: Water, Ground, Rock, Grass, Fighting, Bug
Weaknesses: Fire, Ice (4x), Poison, Flying, Rock