The Spring Tone - Hardcover

Kazumi Yumoto began her career as a writer by writing scripts for operas while attending Tokyo University of Music. After graduation she decided to try her hand at writing a novel for young readers. The Friends, her first book, is the winner of the 1997 Mildred A. Batchelder Award for Translation. It was also named an ALA Notable Children's Book and won the Recommended Book Prize from Japan School Library Book Club.
From the Trade Paperback edition.

i feels herself turning into a monster. Her body is changing, and so is her heart. Since the death of her grandmother, this spring threatens to take away the closeness her family once felt, and brings haunting dreams into Tomomi's home.

The house is falling apart. Grandpa keeps old, useless junk around. Tomorm gets headaches that keep her from enjoying the school break until her brilliant little brother, Tetsu, shares with Tomorm his secret life and his terrible plan of revenge for their neighbor. This spring the real and the imaginary have never seemed so close, and Tomorm must struggle to tell the difference.