The Detective Boys are at Agasa's house when they happen to find a letter from Agasa's first love. Apparently they are supposed to meet every decade but was unable to because Agasa could not solve the code from the letter.
Genres: Animation , Comedy , Crime , Mystery
Keywords: adventure , age-change , anime , based-on-manga , cop , detective , dramatic , japan , japanese-high-school , mysterious , secret-identity , secret-organization , shounen , suspenseful , watch-series-online , watch-anime-series-online