The World Of Demons I Was Summoned To

Reo Riku is a shut-in Otaku who only goes outside to buy food, drink, DVD's or books.  One day, he is walking back to his house after buying some food.  He sees an old man walking down the road, with a truck driving the other way, on a collision course.  However, the truck driver can't see the old man, and as Reo pushes the old man out the way, a pentacle appears beneath him, and he dissappears.