Nini was introduced in Chapter 3 of the Duel Masters: Houden Gachi!! manga series.
A top duelist, in the "Doumei" organisation .
He uses the "Rule of Fire".
He gets Taiga Akaboshi and Minto to air out their ambiguous relationship status publicly. Minto chokes Taiga with his tie after he one-sidedly claims Minto to be his girlfriend.
He has a friendly duel with Taiga.
He seems to be very close to Taiga, being there from the start when Doumei was created. He seems to admire Taiga's team, but ultimately does not join them because of Rion's presence in Doumei.