Partner loses health even just by standing.

[Misti]

I am a newbie to this game, have played it about 5 days already and i have faced such situation.
Before that, as i summoned the partner to help, the partner was losing health as he or she was hit by the monsters, not otherwise.
But starting from yesterday, as i have unlocked Mikami (or how he was called ,that merchant), all partners started to lose health even just by standing. I can summon anyone, stand in the area for 10 minutes and half of partner's health would be gone! Without any reason! Without even being hit by anyone or anything!
And i want to know, is it NORMAL? Or it is some kind of glitch?
If it is, how to solve it? I mean, kinda wanna play with partners, but if they keep loosing health just by "appearing and standing for some times" that kinda...erm...

[Sheiko]

Yep, it's normal for the partner health to decrease after a while of summon.
Merchant, Miroku.
Their health will also recharge if u un-summon them.

[Misti]

Oh, so that is the case. Thank you! Now i am calm knowing it.