Kiseijuu

"Parasites" are tennis ball sized creatures, whose numbers and origins are unknown. They invade and take over the human mind in order to survive. Shinichi Izumi is a 16-year-old high school student who lives with his parents in a quiet neighborhood. One night, a Parasite invades Shinichi's body in an attempt to take control of it. However, it fails to complete the takeover process and ultimately e...