Season 1 - Mirror Twins

Keigo and Yugo play together in a park near their home. Their face look exactly the same, but they are called “Mirror Twins” because Keigo is a right-hander, whilst Yugo is a left-hander, and they have different personalities. At sunset, Keigo asks Yugo to come home together, but Yugo says “No.” Keigo leaves Yugo at the park, and Yugo gets kidnapped. Keigo feels a deep sense of remorse for what happened at the park. 20 years later, an attempted murder takes place and Keigo investigates the case. The only evidence found at the crime scene is the same DNA as his. This makes Keigo to feel that Yugo is still alive and starting his revenge.