Vegeta vs. Trunks? (ベジータの好奇心セルを助ける Bejīta no Kōkishin Seru o Tasukeru, lit. "Vegeta's Curiosity Saves Cell") is three hundred eighty-first chapter of the Dragon Ball manga.
Future Trunks looks over at what Cell is looking at, then he spots Android 18, and Krillin is with them. He realizes they do not know Cell has noticed them, and screams out "Heeeeey!!!! Cell has found you!!!!" Android 18, Android 16, and Kuririn all freak out, and Cell flies toward them. Future Trunks says he will not let him reach his perfect form, then he bulks up like Vegeta and follows Cell. Vegeta thinks it is lucky the androids were here, and then tells Future Trunks he will not let him interfere. Future Trunks almost reaches Cell, but Vegeta kicks Future Trunks away, into a nearby mountain. Cell lands in front of them, and Android 18 and Android 16 prepare to fight him. Cell tells Android 16 not to do anything unreasonable while he is on the verge of shutting down, and says that Vegeta wants him to reach his perfect form, too. Kuririn curses Vegeta.
Future Trunks gets up from the rubble and tells his dad he is mistaken, they can not let Cell reach his perfect form. Cell's power might become far greater than their own, and then what will they do? Vegeta asks Future Trunks if he wants to see how strong Cell will get, and Future Trunks says not at all. He has already seen it enough in his hellish future. He says even if he has to defeat his dad, he will stop Cell from reaching his perfect form. Vegeta doubts he can even attack his own father, never mind defeat him. Future Trunks then lets off a huge two-handed blast at Vegeta, and flies over toward Cell. Cell then uses a Solar Flare, blinding Future Trunks, Kuririn, Android 16, and Android 18. He opens his tail and absorbs up Android 18, and Future Trunks and Kuririn freak out when they regain their sight. Vegeta is surprised Future Trunks really did it, but notices that Cell his changing. He will finally see his perfect form.