Translated. I think I got it all correct, and it all makes sense for Mokou, but it's still kind of a weird way of saying it.

id take the hourai elixir for her that way i could say we'll be together forever literally

Eat her liver. >_>
The way to gain immortality from someone under the effect from the horai elixir is to eat the liver, the person with the eaten liver will still live and regenerate it.

The elixir itself isn't exactly regenerated.
But one who tastes it is never allowed to die. One who eats the liver of that person is too, never allowed to die. It isn't exactly a material thing, but is ruled by the very essence of the matter; unending life.

Does the liver of the person who ate the liver of the person who drank the hourai have immortality properties? Even it doesn't the liver regenerates so theoretically we could have an army of cheap immortals.
I still don't get why Eirin hasn't got on this shit.

She regretted making it. But don't think of it as a material thing. Yes, it does grant eternal life, but it's not a property or anything. In fact, immortality is like casting away the physical body. She drank the elixir and now she can never die. It's not because of the elixir, it's because she drank it.

The elixir doesn't essentially make you immortal in the normal sense. It puts you unable to shift from the state you're at, which isn't necessarily restricted to living. So Mokou, Kaguya and Eirin stay as they were when they drank the elixir for all eternity. But if a ghost or ones such as Yuyuko were to drink the elixir, they wouldn't become immortal in the correct sense but be stuck as a ghost forever, ruining the cycle of birth, death and rebirth.

That's how it goes.

Lick_King said:
The elixir doesn't essentially make you immortal in the normal sense. It puts you unable to shift from the state you're at, which isn't necessarily restricted to living. So Mokou, Kaguya and Eirin stay as they were when they drank the elixir for all eternity. But if a ghost or ones such as Yuyuko were to drink the elixir, they wouldn't become immortal in the correct sense but be stuck as a ghost forever, ruining the cycle of birth, death and rebirth.

That's how it goes.

This pretty much, Since the power to Manipulate eternity and temporality is used to create the elixir. The way that it makes whatever tastes it, exist as it is now in this instance eternally is probably the best explanation. In theory you could use the elixir as quite a horrifying punishment tool. I'll let you use your Imagination on that one.

I'm sorry Mokou, this is pure selfishness on my part. My part in your life will only be a forgettable moment, while your part in mine will take up all of it. However, if you let me become immortal as well... I will gladly suffer the dispair of eternal life, if I'm together with you.