I Summoned the Hero, to the Present Age 大江戸ウメコ

The black history notebook of my middle school days was sent from my parents’ home.
While being nostalgic, as if I had made a proper magic square, I summoned the Hero from another world.
“–Who are you, an underling of the Demon King?”
A story of struggling to return the hero who was summoned by mistake by a 25-year-old OL who should have completely cured her chuunibyou disease.