The youngster has signed on a season-long loan.
"I'm very excited," he said. "I can't wait to see the lads and see the fans, see the stadium. I'm so excited.
"I'll give everything to the fans. I'll show you guys my love, because you guys will also show us love this season, I'm pretty sure. So I'll do everything, and this season we'll do everything to win a lot of games and to stay in the league and make you guys happy and make us happy."
The France Under-21 said of Saints' style: "It suits me a lot.
"I like to have the ball. I saw what the team did last season. Very possession-based team, that's what I like and I think it suits me a lot."
Ugochukwu added: "I think the Premier League is the best league in the world. Every player wants to come over here and play. I had some games last season. This season with the lads, I'm pretty sure that we will do great things. I'll learn from them and I hope they will learn from me as well."