So after making sure that the townies are in fact okay with it (which they are, if grudgingly) he gets them some nice food to go with the party. Zash does his standard special move of "aggressively not being awkward in awkward situations" and the party goes well into the night. And with how no one needs to stay watch (because the plants can do that instead) they all go to bed watered, sated, and happy.

...and Zash stays behind, after the last straggler, after everyone is gone. He spends an hour alone in the diner after everyone's gone to sleep, after he's told Yvette she should go too, after everyone but him and his siblings have long since been accepted into Morpheus's embrace. Just him and his siblings, now.

But his sisters can tell that he wants to be alone, and his brother... mostly can, too. So they leave him alone.

And after about an hour of drinking booze alone in the diner he walks over to the piano, which miraculously survived the destruction mostly intact and then what wasn't intact got fixed on the off-chance that they could eventually sell it. He sits at it. Stares at it.

He spends another hour there, staring at it.

Then he wipes the surface of the piano cover with one hand and pulls it up.

E

A

A

D

A

A

E

G major.

It's been a hundred and fifty years since he's touched a piano.

But he still remembers it. By heart. The song he and Nai composed. He doesn't even need to look at the keys. If he closes his eyes and just... lets his fingers start to move...

Nai's there. With him. In his mind, in spirit. Even before he's physically arrived... he's playing with Zash. Right next to him, with his telekinesis... and then his fingers.

Zash scoots to the side so Nai can sit next to him. They've done this countless times, one started playing and the other joined. Riffed, came up with flourishes, knew exactly what was coming next and played in sync. The song they composed, other songs than that, songs they made up on the spot. They could play for hours, never notice the time passing.

Their sisters loved it. They love music, love listening to it and experiencing people's thoughts and feelings as they play. It's one of the very, very few aspects of humanity that plants can experience in exactly the same way humans do.

And with Nai and Zash they can just... be there. Be together. All of them, all of the siblings, at once.

It's been a hundred and fifty years since he's been in such... synchrony with his twin. Since they've inhabited each other's minds and perspectives so completely, since they've stopped being two people and became a single thing, one soul in multiple bodies, in many hands. Together like this, they're much more than two. Much more than just the individuals that make them up.

And though this began as their song, it's... something else, now. Neither of them wanted to reach the end of the song, so instead they kept playing. They keep playing. They build on each other's feelings, follow each other's thoughts and trail down each other's innermost emotions and secrets.

It's a dangerous thing to do, that. You can't unopen a door, you can't unsee a picture, you can't unhear a word, you can't unfeel a feeling.

You can't unkill a person.

[...Zash—]

[I heard you. everything you said, that time.]

[why, Nai?]

[why what, Zash?]

But like this, here, he knows the answer to that question, obviously. There's no point in asking except to bring it to focus.

The song gets faster. More forceful. Angrier.

[why did you become Knives? why was Knives someone you wanted to be? why was Knives someone you could be?]

Knives is the person Nai becomes after decades of honing himself into a weapon and cutting out everything that's not about rescuing plants. He's the person Nai becomes after trimming the fat in his personality and habits and thoughts and feelings whenever they didn't serve the purpose of rescuing plants, while at the same time nurturing and sharpening and encouraging all of the habits that made him more effective at it.

[a weapon, Nai. why... how... are you a person who can become a weapon?]

[how can you say that you might do it again? that you might keep killing people, when you know how wrong it is, I know you know, I've seen it—]

Because no one else would stand up for his sisters. Because not even his brother would, they themselves most certainly wouldn't, and the idea of watching all of them be fed into the all-consuming hungry maw of humanity for decades until they were all dead, and then watch humanity not even survive after that because there's no way they could survive without plants, would kill him.

[I didn't have a choice. I don't have a choice.]

[that is bullshit and you know it! you always have a choice! I've been choosing something else for a century and a half!]

[you're wrong. you haven't been choosing. you have been doing the opposite of choosing. you say that—]

If humans want to decide that other humans live or die, well, that's a lot more fair than if he does. He's not human; it's just not his place.