Tao is what powers you and the other tensens. They're able to withstand immortality because of it. It's crucial to your life. For something so important though, it's easy to obtain. Practicing bochu jutsu is all it takes.

You were quietly walking through the forest when Ju Fa suddenly grabbed your wrist, having caught up to you in a small opening in the forest. "My tao levels are feeling low.." he grinned, pulling you closer. "You'll help me, right?"