Meatball Machine (1999)

Grease monkey Yoji works in a small shop. The best part of his day is watching the cute Sachiko walk by during his breaks. He never feels he is good enough to chat her up however. He comes across an alien parasite and, not knowing better, takes it home. He intervenes a few days later when he sees another grease monkey talk up Sachiko a few days later. The two become friends and she finds herself at his place soon. The parasite takes Sachiko's body over to start.