My sudden improvisation with the kiss somehow worked out, thanks to Ethan's quick thinking.
"Lil... Julia...?"
"I'm s-sorry, Leon. I just wanted to be with you until the very end."
"...If that's your wish, Julia, then drinking the poison left on your lips to die with you is a death I can be content with."
"I'm sorry, Leon. I was selfish, and now you're suffering because of me..."
"It's alright, Julia. If it's what you wanted, my decision would have remained the same. Dying while embraced by your warm lips is a far more graceful death than I deserve."
"...In our next life, let's be together, Leon."
"...Yes, Julia. In the next life, for sure."@@novelbin@@
Thud.
In this way, we managed to alter the final scene, where I was supposed to hand him the vial, by implying that the poison remained on my lips.
The most important part of the ending was that both Leon and Julia drank the same poison and died together. Afterward, the play moved on to the epilogue with the other students performing their roles, and the play of Leon and Julia, which almost ended in disaster, was brought to a close.