Aruna Kinoko

But the yo-yo master said nothing, he just kept yo-ing

Name was Toska, now is Aruna Kinoko ! his monster name works too

He has a yo-yo,

He's a jackalope satyr man and all his special abilities are yo-yo tricks. I think he might be a spellcaster? He's a spirit monster

Flying Trapeze allows him to hit your opponents life points directly.