User blog comment:Koishi-Komeiji/Yachiyo Nanami/@comment-405747-20190909191741/@comment-24965192-20190911154644

She's strong gameplay-wise enough to become a 4* and she's also popular as a character, further boosted by her status as a main character.

Mifuyu is a 4* Assassin. Not all triple Arts Servants need to be NP spammers.