Optional Bosses (First Game)

Slimamander
Encountering: Fought during the "Triple Trouble Side" Quest

Sproink
Encountering: Fought during the "Burst Your Bubble" Side Quest

SV Snaggerjag
Encountering: Fought during the "Hooked on Battles" Side Quest

Massiface
Encountering: Fought during the "Ghost Squad Part 1" Side Quest

Phantasmarai
Encountering: Fought during the "Fight at the Museum" Side Quest

Tarantutor
Encountering: Fought during the "Ghost Squad Part 2" Side Quest

Dr. Maddiman
Encountering: Fought during the "Mad for Power" Side Quest

McKraken
Encountering: After beating the game, you can rematch Lord Enma in the Yo-kai World. After doing this, you can access the McKracken Fight

Duwheel
Encountering: Fought during the "Adventure Squad Episode 1-Abandoned Tunnel" Side Quest

Chirpster
Encountering: "Fought during the "Don't Count your Chickens" Side Quest

Gargaros
Encountering: Yokai Watch Blasters or Get three Crosswalk Penaltys

Orgalus
Encountering: Yokai Watch Blasters or use the crosswalk correctly 20 times in a row

Orcanos
Encountering: Yokai Watch Blasters