Eita Sasaki

Also Know as:
Princess Ruri/Ruri-chan (in-game character's username)
Relatives:
Runa Sasaki (younger sister)
Age: 19
Occupation: Part-timer on a Café; College Student
Affiliation: Chocolate Rabbit Guild (Guild Master)

Eita is Yamada's best friend and loyal online gaming partner, with whom they formed a guild. He views his character not so much as a self-insert avatar, but as a female alter ego that embodies his ideal loved one (parent, sibling or lover), so Akane didn't immediately recognize him in real life until Eita revealed his in-game identity himself.

In episode 4, it is revealed that he based his playable character on his younger sister, as he idealized her incredibly.