Mann then signed with Sengoku Raiden Championship in Japan, to participate in their Featherweight Grand Prix. In the opening round, Mann faced Tetsuya Yamada and defeated him via unanimous decision (30–29, 30–29, 30–29). During the first round of the fight, Mann was able to land powerful punches, before falling into a deep kneebar attempt from Yamada. After escaping, Mann was able to gain top position to end the first round. The second round saw Yamada attempt a standing Kimura, which was fought off by Mann, who was later able to take down Yamada twice, whilst fighting off a second kimura attempt. The final round saw poor kickboxing attempts by Yamada, which was countered by two takedowns. Finally, Mann looked to utilise an ankle lock, which was reversed into another kneebar by Yamada. After the third round ended, Mann was declared the winner via decision.
