The story starts off with the MC defeating the demon lord or something. After that the MC says farewell to a bunch of characters, and when he returns to his world, he meets up with his friend that's a girl in a fast food restaurant, who notices that the MC is giving off a different vibe. When he returns home he unconsciously uses magic, realizes he used magic and is confused since he's back in his world. This all happens in like 2 chapters.
You are looking for Kikanshita Yuusha no Gojitsudan
In a fraction of a second, a university student, Kashiwagi Yuuya was summoned to another world and came back. Time didn’t pass in Japan, but Yuuya has completed the quest as a hero in another world and successfully returned. But to his surprise, he still retains his powers as a hero. Thus started the unordinary life of a hero in the present day.