This invention is a parody of the series Kamen Rider Double. This process happens by creating a fusion of two subjects. multiplying their skills but the fusion is shows half of each subject.
When two subjects bring this into their heads, do a fusion movement, and shout, "keron cross!", causing a fusion and combining their skills. Each half of the fused subject is , when Keroro and Tamama fuse, they have their own voice but Keroro says "desu" and Tamama says "de arimasu". This invention can also merge mergers already made.