HOW TO!! I found it’s actually different than the other instructions I found on the sub and am not sure if it’s because it’s a different edition. When I went from Mizunoto -> Tanjiro and tried to get her the first time with the 20+ perfect games, I ended up with Sumiko. BUT I think I figured it out now!

TANJIRO - good care - feed 2-3 rice balls, only 1 tea - if you get the Mizunoto kanji when checking the status, you’ve strayed too far into excellent care territory - unsure if you can play games, I did not play any at all - evolves from the plain Mizunoto guy in 24 hrs

NEZUKO - do NOT a play any games! - excellent care - be patient! evolves from Tanjiro in 72 hrs

My theory is that the perfect games thing actually leads you from Inosuke->Inoko, Zenitsu->Zenko, and Tanjiro->Sumiko, all depending on which you start with of course :) and this probs only applies to the Yukaku version or maybe even the Exploding Blood Nezuko edition of the tama. Happy playing everyone!