Chakra already includes mental/spiritual energy that comes from the mind. That covers things like
will, intent, and emotions, which fall under Yin.
That’s why in the series you see characters get stronger or push out more chakra based on their resolve or emotional state (like the
Will of Fire, rage amps, etc.). It’s not separate from the system it’s already built into how chakra works.
So I don’t really get the argument that Haki is some special “will-based energy” when chakra already operates on that same principle Chakra just covers all and more that's all.. In Naruto chakra also makes it possible to manipulate your very own will Black Zetsu is the manifestation of Kaguya’s will, created through advanced chakra manipulation (Yin–Yang Release), where mental/spiritual aspects are given form.
We clearly see that emotions play a role in chakra as well, which shows that chakra contains all aspects of mental/spiritual energy, not just experience or thought. It includes will, emotions, intent, and overall mental state.
Emotion is what you feel
Will is what you choose to do with it
Will isn’t a separate energy type, it’s a component of mental/spiritual energy, and it can show up in different forms like conscious intent, emotional drive, inherited beliefs (like the Will of Fire), or even instinct.
- Emotion = state (anger, fear, love)
- Will = direction (intent, resolve,)
- Haki = manifestation/output of that will
https://imgur.com/a/HtqZQ39
https://imgur.com/a/9PZmm9x
https://imgur.com/a/juZdh7O
Chakra being connected to life force/physical energy (isshiki seeing his remaining life force as chakra)
https://imgur.com/a/I3onyOl
Nature energy/chakra the very energy in the world and Naruto can sense it.