A father is talking to his kid about their plans tomorrow and says,
(The sentence is supposed to say, "Kenshin, would you like to go to shopping with dad?" Obviously, not a one-to-one translation)
Aren't both sentences the same? I can't see the second sentence not relaying the idea of "together". So what does the 一緒に do exactly? It seems, to me, that the sentence doesn't really need it.