From Impossibility:

Miharu Tsuji is a 15 year old tom-boy who finds out that her best friend likes her. Now, she must deal with the different emotions and find out what she truly feels in this all-so-strange situation.

Contains three stories.

[From Ivyscan]:

Story 01: Chimi is impatiently awaiting spring and her 14th birthday. Not yet ready to give up her tomboy ways, Chimi has a lot of confusion to deal with when she feels the first stirrings of girlhood awakening inside her.