Denja is a wanted criminal in 22nd century for bank robbery. During escape, he gets into an accident and has to be hospitalized at the same hospital that Doraemon went for checkup. With a help of Substitution Rope that is (conveniently) stuck out of Doraemon's pocket, Denja is able to swap his body with Doraemon's and escape the Time Police's detection as the Police chase after Doraemon in Denja's body instead.
After he feels Nobita's kindness toward him, he decides to reveal his identity to Time Police, switching his body back with Doraemon and allow himself to be arrested without any resistance. Denja is then taken back to 22nd century but not before Nobita tells him that they are friends and wants to play baseball again, which makes him shed tears.
At a glance, Denja might be a heartless and violent criminal who cares about no one but himself. However, these hide Denja's caring personality, which can be seen when he gets into accident just to avoid hitting a dog on the road. Also, his mean personality comes from him being abandoned by his human partner and believing that humans are nothing but cruel. This perspective is changed when he meets Nobita while he is in Doraemon's body as the latter say that he felt sorry for Denja when he was abandoned.
At first, he never cares about Nobita. After he helps Nobita practice baseball, Denja receives a thanks from Nobita and realizes about his mistakes he made before.
- He has his air cannon upgraded.
- He is very good in fighting
- Denja has the same pronunciation as Danger. It might be the source of his name.