REBORN! Season 1 Episode 12 Master's Training! Strengthening Program.

When Nana tells Gokudera to take care of Tsuna, Gokudera is glad that he's been acknowledged as Tsuna's right-hand man. But when he is unable to protect Tsuna from bees, Gokudera is embarrassed, and Reborn suggests taking the Vongola Strengthening Program. Gokudera and Yamamoto end up getting special training from Reborn, but Gokudera is jealous of Yamamoto and is intent on proving himself to be the best candidate to be Tsuna's protector. Gokudera can't let down now, because Yamamoto is acing the training program