Eto Eto (Sage Mode)

Key: Another Etro
Character: Eto Eto
Skill(or transformation): Sage Mode

How well do you know the source material?(obviously not relevant if it's a transformation): Senjutsu Chakra is a source of energy that nature produces, it exists all around people and some animals tap into it to increase their physical abilities. Most users that tap into this type of energy must reach certain conditions to use it, such as extreme levels of energy, remaining entirely still to absorb it successfully and their bodies must be strong enough to support the power of the natural energy. There are also incomplete versions of Sage mode that are likely to give you an animalistic trait while being weaker than the normal along with some perfected Sage modes still giving you animalistic characteristics.

Reasoning: After the hard-fought and ruthless battle with Kaguya and Rym, Eto Eto had lost a vast amount of people she used for entertainment, and friends she didn't know meant so much to her. Her dear friend Rosemary who her crush found worthy of protecting at the cost of his own life and time with Eto herself, and her beloved Sage who had brought the gift of new experiences and romantic feelings that she hesitantly but eventually accepted. The spark of excitement, joy, and comfort appeared to have gone with them when they died, a lingering sense of desolation in their place even though the warmth and comforting presence of Sage remained somewhere within her.

Scattered and somewhere within, Eto felt everything was her fault, and if she had acted properly and handled Kaguya with Sage's assistance once she had shown signs of not being willing to understand others, things would have turned out fine. The thought of this haunted Eto constantly and only served to make her feel more lonesome, though trying to heal this, in the end, has only served to make it worse. When people surrounded her, she felt alone, and when in the company of friends, the lingering feeling of misery and loneliness grew stronger.

The only comfort was solitude, and so she took her time to embrace it, becoming quieter, her interactions with people becoming less energetic and pleasant as she took more time to herself. Watching and testing Saints nearby while attempting to carry out duties she believed to be only right due to her hand in Sage's death. What was she supposed to do now with everyone gone and people only serving to make her feel worse?

Effie wanted to train Eto, and so, she took her lessons and after learning from them returned to embrace her loneliness once again, now with the gift of sensing energy and moving at incredible speeds far above what she once was. Eto began checking on the Saints and Dragons from time to time due to her wishing not to lose more beautiful and exciting life and instead understand it, but she still didn't feel the same joy when doing so as she once did.

The guilt and misery plague the Yokai, the memories offer comfort and joy but eventually stirred the feelings of desolation once again, causing her to become attached to them. Eto began hanging out in places her beloved friends and crush once remained, and she sat in them alone as she focused her incredible manipulation of energy in hopes of discovering Sage's tricks, reading minds, and feelings while living in her memories.