Dream Saga Series by Megumi Tachikawa

Yuuki Wakasa is a typical 5th-grade schoolgirl who dutifully helps her mother around the house by taking care of her three younger brothers (a.k.a. the "monkeys"). She's often found escaping to her room at any given chance to read manga, which her mother thinks she does too much of! However, when Yuuki finds a red magic stone she also discovers she's the 'chosen one' who must enter the world of dreams in order to save the Sun God from destruction.

Yuuki Wakasa is a typical 5th-grade school girl who dutifully helps her mother around the house by taking care of her three younger brothers (a.k.a. the monkeys). She often escapes to her room at any given chance to read manga books, which her mother thinks she does too much of! However, when a red magic stone mysteriously falls from the sky, she discovers that she is the "chosen one" who must enter the dream world to save the Sun God that shines in both worlds from destruction.

The quest to save the two worlds turns into a tangled web when Yuuki and her companions discover they need the Shinkakyou to get to the Sun God. Soon they stumble upon the crystal snake--and it's throwing a hissing fit at Takaomi! However, this serpent in the grass may turn out to hold just what they need to get to Sun God!

The fate of the two worlds is at stake, and Yuuki is the only one that can save both worlds! It's a big-scale adventure as the crystal snake slithers to the surface and Takaomi decides to be the hero and try to defeat the serpent. All the while, Yuuki's feelings for Takaomi are growing stronger by the day. Will she finally tell him how she feels?