Kobayashi debuted on September 11 at , introduced by William Regal, where he announced his new ring name, "Hideo Itami", meaning "Hero of Pain", and fended off The Ascension when they interrupted the segment to confront Regal. Itami made his in-ring debut at the following day's tapings of "NXT", defeating Justin Gabriel, after which he was attacked by The Ascension. During the following weeks, Itami kept engaging The Ascension in brawls, but continually lost due to the numbers disadvantage; the storyline was that as a newcomer in NXT, Itami did not have any friends in the locker room to help him. This continued until November, when Finn Bálor debuted as Itami's new partner. After weeks of feuding with The Ascension, Itami and Bálor defeated them at on December 11. Itami then participated in an NXT Championship number one contender's tournament, defeating Tyler Breeze in the first round, starting a feud between the two. He suffered his first defeat in NXT on January 15, 2015, when he was defeated by Bálor in the semi-finals, thus eliminating him from the tournament. At , Itami defeated Breeze in a rematch. They continued to exchange victories over each other until Itami lost a two-out-of-three falls match to Breeze on the April 1 episode of "NXT" to end the feud. On March 27, Itami won the WrestleMania Axxess NXT tournament by defeating Adrian Neville and then Finn Bálor to get a spot in the André the Giant Memorial Battle Royal on the pre-show of WrestleMania 31, where he was eliminated by eventual winner Big Show.