You're confusing the time system and the human/youkai gauge, though the two are related.
The H/Y gauge will go in the direction of whichever side you are while shooting. Killing enemies and picking up the time orbs gives a large boost in your current direction. The best way to quickly adjust is to focus kill enemies with familiars, as they drop a lot of time points - you can then switch back to human or stay as youkai to get the gauge where you want it. Given the masses of enemies with familiars, this isn't too hard.
As for the time system, again focus killing enemies with familiars is the largest source you can expect during the stage. You get time points for shooting when 80% human or more, but only get time points for grazing as 80% youkai or more on bosses. That said, staggering kills of enemies with familiars (make sure they get them out, especially on stage 2) will both clear lots of bullets for you and get you oodles of time points, as you shouldn't have any real problems hitting the requirement for each level if you play it smart.
