Well, you can't get an Umbreon on Pokémon Leaf Green... since it doesn't have a clock (Umbreon evolves at night time).
So the only way is to trade it to Ruby/Sapphire/Emerald.
There, you raise it to max friendship and make sure the clock is on night time. Raise it a level, and your Eevee will evolve into Umbreon.
But this is only if you can trade...so, it's actually impossible if you can't trade.
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you can't get mamoswine in Pokemon leaf green because it doesn't exist in leaf green
behind the door is leaf green u enter the Pokemon leaf green world
She does its either Leaf or Green.
Umbreon is a Dark type pokemon.
no you cant get umbreon since the only way to them is to evolve them at. night but you can get espeon by training him until your friendship is strong or at its best and trainig him. you can check how strong youre friendship is in the place where you start the game in garys house talk to his sister and she will tell you PS she only tells you if you've already beaten the Pokemon league