Kagaku to Mahou no Kasou Sekai Vol. 1

Protagonist Akira Kido and his classmate were into a VR game called Fantasia.
In that world Akira was finding out the details of being a spellcaster when he met a young girl.
She ran off, so he asked a red-haired boy where she went. A blue-haired boy suddenly appeared, then those boys also ran off.
Thinking it was odd, Akira contacted the support staff and used his magic to chase after them.

[From DLsite English]