From FairGame:
"Live with Sincerity" is Natsuki Taiyou's motto. It's first day of high school and Taiyou was heading to a school and Taiyou meets Hinata during the way there. He fell in love at first sight and suddenly confessed to her. Her answer was yes and she runs away without saying who she was, but it turns that she was her classmate. Taiyou felt a destiny between them. However, on the next day, she doesn't remember who he is. why could it that be...?

The Soul Score... that is something not unlike the threads of fate which tell the story of a person's life from the minute they are born to the finale of death. Few people can see this score, even fewer can manipulate it.
After being hit by a car and nearly killed, Kyosuke Hibiki can see and hear this mysterious soul score. Soon after, he meets a girl named Tena, a "tuner" who is able to manipulate the score and remove discordant notes to bring it back into tune. Tena is determined to make Kyosuke her pet, but Kyosuke is none too fond of it. Yet, the two begin their dissonant duet...
(Source: Manga-Heaven)

Sawamura Soushi is a soldier in a war-torn future. He meets a cute, innocent young girl named Nadeko, with whom he starts up a friendship. Nadeko is a flower girl, one of the girls who has a flower growing from her heart. One day, when Sawamura is trying to protect her from danger, she confesses her love to him and protects him with the plant growth that suddenly comes forth from her body.

Sawamura soon learns that there is a special squad of flower girls and their partners, and that their abilities are awakened when they fall in love. But does he really love a girl that is a decade his junior, and will he be willing to be a good partner for her? What's more, he learns that the awakening also starts the growing of the flowers in their bodies, so that the flower girl soldiers have only a short while longer to live. How can Sawamura and Nadeko make the best of such a terrible situation?

(Source: MangaHelpers)