Obtained from Youkai Island Onigashima Event.
A very powerful Sub for any Slash Card! Momotaro grants a 30-35% Skill Boost to any Slash Card. What's more, if your target is a Youkai, the Skill Boost becomes a solid 35%.
The Youkai condition won't come into play much, but Momotaro is a fantastic Sub for any Slash Card nonetheless.
Also of note, you can Sub the Magic Hammer from his Event to give the ability to Prevent Enhance Linking.
- Magic Hammer: When Main Card's Skill Activates, grants (+1/1/2) ATK (When subbed alongside Momotaro, grants (0/33/50%) Chance to not Link with Enhance Cards)
With two SSS Magic Hammers + Momotaro, this gives you roughly a 75% Chance to Prevent Enhance Linking.