Please don’t apologize! I enjoy answering them. I’m just slow about answering questions in general, haha.
Sakura and Syaoran never stop being an item from the age of 11 to their eventual deaths, so there’s never really a question of whether or not Syaoran will ask Sakura to marry him, but a question of when.
Syaoran spends - literally - 15 months looking for the perfect opportunity. He wants to wait until they have both finished whatever schooling they want to complete. Then he wants to make sure he has stable employment: if he can’t find a job in Japan, he’ll have to leave when his student visa ends, and that will put a damper on any wedding plans. (Syaoran is independently wealthy through his family, so money is no real object, but Japan’s Immigration Office isn’t going to accept his inheritance as an excuse for not contributing to Japanese society.)
Syaoran gets the engagement ring custom-made: small pink diamonds arranged in the shape of a sakura flower, surrounded by tiny emeralds*. It’s not very ostentatious, but he hopes she finds it to her taste more than finds it striking. She likes small, cute things best anyway.
He needs to pick the perfect setting. At first Syaoran thinks he should just carry the engagement ring with himself for a while and when the perfect mood arose, go to one knee and propose then. But there’s two problems with this idea:
1) It goes against his sensibilities to not carefully plan out the proposal, and
2) Tomoyo insists that Syaoran tell her the time and day so that she can get it on video. Of course.
Finally, he settles on proposing on Sakura’s birthday. After having breakfast with her family and lunch with her friends - Sakura is careful to equally share herself amongst her loved ones - Syaoran finally has her alone for dinner. He proposes they go for a walk under Tokyo Tower afterwards. They reminisce about fighting Eriol in its shadow. They stop to look up the Tower; the moon breaks out from behind some clouds. Some bushes rustle.
The moment is perfect. Syaoran takes a deep breath, turns to Sakura, and says her name. She looks back at him. He takes her left hand in his, reaches into his jacket pocket with his right hand, and goes to a knee. He pulls out the ringbox. He opens his mouth.
Nothing comes out.
Syaoran’s heart won’t stop pounding, so loud in his ears that he doesn’t think he would be able to hear himself even if he could speak. His face is burning. Sakura says ‘oh!’ and stares first at the ringbox with round eyes, then at him, turning bright pink and bringing her free hand to her mouth.
Ten terrifying seconds elapse. Then Sakura cries, “Yes! Of course I will!”
She falls to her knees and grabs Syaoran around the middle, hugging him tightly. Syaoran, stunned, hugs her back stiffly. She kisses him, hard, and Syaoran finally manages to breathe again (through his nose). Once Sakura pulls back, Syaoran finally opens the ringbox and put the ring on her finger, which she’s very pleased with. They sit there on the pavement, both of them trembling, and Sakura laughs and Syaoran smiles. They can’t even stand for quarter of an hour, and Syaoran is rendered all but mute by emotion. (They might both cry a little.)
(The shaking bushes stop shaking only after they get up and leave. Tomoyo never shows anyone the video; some things are best kept to oneself.)
*Diamonds are the birthstone of April. Green emeralds represent Syaoran (because he likes green).
Full disclosure: this is heavily inspired by knightarcana. :D