The abrupt and, at the time, inexplicable resignation of Prime Minister Shinzo Abe in September stunned the nation, prompting criticism that he was an irresponsible and immature politician who couldn't even offer a convincing explanation as to why he quit the nation's top post.

Abe finally confessed publicly Thursday that fear of a recurrence of a malignant bowel disease — which forced him to visit the bathroom up to 30 times a day — prompted him to give up his prime minister's post.

Specifically, he suffers from ulcerative colitis, a chronic inflammatory bowel disease that causes pain, diarrhea and often bleeding, and can lead to other serious complications. Its causes are still unknown and pose great physical and mental burdens on the patient.