Sumika Fujimiya

Takafumi's childhood friend whom he reunited after being separated for long time. She has a crush on Takafumi (of which he is oblivious to). After finding out about Yousuke's magic ability the moment she came into Takafumi's apartment, she starts spending her days at Takafumi's apartment and together, they spend their days watching replays of Yousuke's adventures in the other world.

(Source: Isekai Ojisan Wiki and Wikipedia)