Complex sentence: After the pilots are tricked into killing the Alliance leaders, and he loses in a duel with Treize, Wufei begins to severely doubt himself, and eventually returns to train more with his master, Master Long Shirin.
Split into simpler sentences: After the pilots are tricked into killing the Alliance leaders and he loses in a duel with Treize, Wufei begins to severely doubt himself. He eventually returns to train more with his master, Master Long Shirin.