OT's former mascot.
She(?) was a poster named after a trap that used to like to talk about traps, and other "Kyoot" things (including some curvy moes at times). Claims to be a large black man that could bench press more than you.
Somehow Seiko developed a cult following and ended up becoming OT's mascot. She has since left and closed her account, but the nickname OT-kun lingers still.
Was probably Gigglepuffy / Masters Keaton, considering his love of making fake accounts and their similarities in trap obsession. May also have been Sarumanu, who may also be Gigglepuffy.