

Alright guys, here me out.
Maybe Lumalee wants to die because he wants to be with his brother again.
Here's what I'm thinking.
I'm thinking that Lumalee save Luigi's life from the Blast of King Bob-omb, when Lumalee is about to die, Luigi comes to aid him telling him that it's gonna be OK, but Lumalee tells him that it's alright, he'll be fine, when Lumas die, they can be reborn again, he might not remember Luigi, but no matter what happens, he'll always be his best friend, and that he'll always be in his heart, then says goodbye to him, he finally filled his purpose by launching in the sky, turn into stars, and suddenly a 1up lands in front of Luigi, Luigi gets emotional, and says he'll never forget him.
Let's just say that while Luigi and the others are in their cages, Luigi finds a way to escape, he makes an alliance with the Penguin King, the Penguins, and Lumalee (I've decided to make Lumalee join them, because let's just say, after Luigi ask Lumalee why he wanna die so badly, Lumalee tells Luigi that it's his purpose, then Luigi makes a deal with him, if Lumalee can help him free the Penguins and help them escape, he can help him with his purpose, right after all this is over, Lumalee gets happy and agrees to help him.)
After a while, Luigi bonds with Lumalee. After Luigi asks again why dying is so important to him, Lumalee explains that he wants to die so he can be with his twin brother "Mari".
Mari sacrificed himself to save Lumalee. After he lost his brother, he's doing whatever he could to be with him again.
Then he explains why he got locked up. (I don't know how to explain that)
Lumalee also explains that he hasn't had any friends ever since he left home to look for his brother.
Luigi feels bad for him.
Then I decided to make him and Lumalee best friends because they also have something in common, like they both have brothers and have "Lu" in their names.
What do you think?