Can someone write me a long story about a love triangle? (school appropriate)

Kellan's heart thumped as he held the box in his hand. Saying 'thumped' is a bit of a stretch, as it was basically trying to hammer its way out of his chest so it could find its soul mate. The heart of the one person he was holding the box for. He'd planned to surprise her, and his heart pounded even more intensely as he neared the house. The path before him seemed to stretch out. He tried to take a breath but ended up choking on his own spit. Anticipation drew beads of sweat from his brow, and the ring inside the box condensed, becoming at least eight tons in his palm. This was not at all like the movies. Proposals in real life were downright terrifying. Just four simple words. But he couldn't do it. Kellan swore under his breath and forced his legs to obey. Just do it. Just do it. The door was unlocked, which meant she was probably in the gym throwing jabs at a punching bag. The cinnamon scent of the house brought an image to his mind. The image of the girl he'd fallen right into. He'd memorized every feature of Millie. The dark skin, startling emerald eyes, and that smile where one corner of her mouth was higher than the other. Hopefully that smile would still be there when he asked. He turned into the corner of the hallway, and there was that smile. But she wasn't smiling at him. She was smiling at somebody else as she held him in her arms, the way she always used to hold Kellan. She looked up and noticed him standing motionless at the threshold, his face blank. Her smile dropped.

"Kellan", she stammered. "I - "

The man cut her off. "Hey, you lost, pal?"

"Yes", Kellan replied tonelessly. "I must have gotten the wrong address."

His hand relaxed, and the box clattered to the floor. The diamond encrusted ring rolled out from the gaping box and came to a stop at Millie's toes. All emotion had drained from Kellan's face. He walked out the door without another word with his back straight, his head held high.

personal narrative

first person fiction

etc.