In this world, when human beings reach the age of 12, their bodies gradually change to the genders they wish to be. And by the time they are 14 years old, their appearances change to reflect their genders. But by spring of my eighteenth year, I am still without a gender...

(Source: MU)

From The Zero Alliance:

Wisdom brings good fortune; but wisdom that is too advanced to humans bring destruction.
Ox and Ivan, a pair of “wisemen”, are on a journey to collect wisdoms that are in the wrong hands.

A war rages through the city, where battles are fought with music. Theo is disappointed by his brother Will’s refusal to take part in the war, despite his talent for composing battle music, and decides to take matters into his own hands by using the music Will has composed.
(Source: MU)

Ren travels all the way to the City of Music, Vienna, to study music. Her classmates are all musical geniuses, but they also come with problems!

(Source: MU)