Yamaiko

Yamaiko (やまいこ) is one of the three female guild member of Ainz Ooal Gown and regarded as one of the 41 Supreme Beings by the NPCs of the Great Tomb of Nazarick. She is the older sister of Akemi and the creator of Yuri Alpha.

Background
Yamaiko and her younger sister, Akemi played YGGDRASIL together. However, Yamaiko picked as a Nephilim from the heteromorphic race while her younger sister choose to be an elf.

The Bloody Valkyrie Arc
Ainz remember that he gambled his entire bonus away just to obtain the Shooting Star. Amongst all the guild members, he and Yamaiko, are the only two possess this item.

The Men in the Kingdom Arc
Ainz reminiscences about the argument between Touch Me and Ulbert Alain Odle. Touch Me remembers that Yamaiko needs a rare drop from the Fire Giant Boss but she doesn't particularly need it right now before the continuation of the argument between Touch and Ulbert.

Momonga
Back then in YGGDRASIL, they used to chat about private topics. However, due to the passage of time, Momonga seems to have forgotten a lot about it, which is something he regrets. Every once in a while, when trying to teach the guardians, Momonga wonders what Yamaiko would do in such a situation, showing he still respects her skills as a teacher.

Akemi
Akemi is Yamaiko's younger sister.

Yuri Alpha
Yamaiko is Yuri Alpha's creator.