Let's Go with Komasan: First Massage (Japanese: コマさんといく ～はじめてのマッサージ～,Komasan to Iku ~Hajimete no Massāji~), It's Summer! At the Beach! With a Yo-kai! Gurerurin (Japanese: 夏だ、海だ、妖怪だ！ グレるりん編,Komasan to iku ~ hajimete no tōgei kyōshitsu ~), and It's Summer! At the Beach! With a Yo-kai! Swosh (Japanese: 夏だ、海だ、妖怪だ！ うみぼうず編,Natsu da, Umi da, Yōkai da! Umibōzu-hen) is the 79th episode of the anime series.
Komasan visits a place, so he can get a massage. While Katie changes into her swimming costume, Yo-kai Roughraff make Nate, Bear and Eddie overthink of her swimsuit. Later on, the trio gets inspirited by Swosh and the waves wash their trunks away.
Nate and his friends visit the beach, with Yo-kai Roughraff and Swosh there. Roughraff make Nate, Bear, and Eddie daydream of what Katie's swimsuit will look like, and Swosh makes Eddie very cool about things, even a bird pooping on him. Nate has Swosh inspirit him and Bear, and they act cool too. However, their swimsuits soon fall down, and Swosh makes them not care. Whisper tells Nate he can't be in the ocean naked, so he finds a plastic bag and wears it instead of swim trunks. Bear and Eddie soon do the same and use Seaweed and a Shell. Bear switches to a crab, and Nate switches to an Octopus. Bear and Eddie soon use an Octopus. Swosh leaves and gives Nate his medal, then Nate, Bear, and Eddie are shocked about what happened.