In order to change from human form to weapon form, a Demon Weapon must picture the weapon dormant within their soul and concentrate to perform the transformation.
Sometimes, the Demon Weapon may have difficulties in transformation at first but with a lot of training they would be able to transform at will with ease. In some cases, a demon weapon transformation could be incomplete due to psychological issues. An example of such case is, Tsugumi Harudori's halberd form which lacked an edge because of her insecurities and lack of self confidence. However, eventually, she was able to produce an edge because of her newfound confidence and strong will.
- ↑ Soul Eater Prologue #1