Fun Fact: These two anime take place in the same universe / Anime (RDR, Reshotka Democratic Republic) :: фэндомы

Yakusha Kure from Dumbbells is related to one of the characters since she’s the mother of a side character in Kengan. And her black sclera and exceptional physical abilities is because of a plot point in Kengan, ages of selective breeding that the Kure clan performed which resulted in supernatural abilities that most of the Kure characters in Kengan are capable of.

Not to mention, they constantly make references to the other series, for example, in an extra Chapter in Kengan Ashura, Julius ran out of Protein Powder, so he went to the Silverman Gym in Dumbbell Nan Kilo Moteru and acted in an advertisement with Macchio for some. Or in Dumbbell, Akaya's family owns a gym, whom one of the fighters, Gaolang Wongsat frequently trains in.

Ну и ещё позволю напомнить, что у обоих произведений один автор.