Issunboushi (OVA)

As a poor college student struggling with a heavy workload, Tomo Issunbashi passes out due to a combination of overwork and malnutrition. While Tomo is unconscious, one of his ancestors appears before him and, disappointed in Tomo's pathetic condition, promises to do something to improve his life. However, when Tomo awakens, he finds he has shrunk to a fraction of his normal size! Now completely helpless, he has no choice but to let the women in his life toy with him as much as they wish.