yatteyan'yo
A line spoken by Soga no Tojiko in the Touhou series video game Ten Desires.
It is one of the lines spoken when she and Mononobe no Futo are summoned during Toyosatomimi no Miko's spell cards. It can be translated as "I'll take you down!" but is a rather odd way of saying it. As such, it has become her catchphrase among the fandom.
Since Tojiko and Futo are summoned at the same time, their phrases are often said together.
Futo's phrase is "われにおまかせを!" (Ware ni omakase wo!), and translates to "Please let me handle this!" or "Leave this to me!"