Senjutsu is the power to sense and control the flow of life force in living beings. It can deal interior damage to others by disrupting or severing the life force of their opponent's, and it is also capable of bypassing conventional defences, preventing others from using their own abilities, and forcefully putting others to sleep. It can also be used to seal away other beings, and advanced users could even master esoteric techniques like increasing the luck of others by controlling the flow of their life force or to grow older temporarily, gaining access to powers that would only be available in a more matured state.
It can be used to remove curses, poisons, diseases, or just bolster their life force for a regenerative healing effect. Meanwhile, it's not the best at rapid healing, it's also capable of healing esoteric damages like restoring lost lifespan or otherwise hard-to-detect hidden injuries.
It also gives the user the ability to sense and perceive life force, which, even at the most basic level, allows for locating living beings and giving a basic read of their general wellbeing. At advanced levels, to sense the presence of Sacred Gears in people or read the movements of others just from their aura.
Senjutsu heavily relies on an understanding of nature, so most of the techniques are related to it, like manipulation of mud, earth, and plants, but it struggles with manipulation of the artificial.
Normally, all Senjutsu users are capable of learning Touki as it forms a complete power system, but for this CYOA, it is treated as a separate power, which makes you incapable of learning Touki just from Senjutsu, unless it is purchased.