Ohayo Gazaimasu,

I have a question:

Are archers that skillfull to fire an arrow on an ennemy without any chance to harm an ally who fights the same ennemy in melee ?

let's have an exemple: Lion fights one bandit.

At range 4, Kaito fires an arrow on the same bandit.

Well either the kamis favor the archers or there is a gap in the rules ...

You can houserule it in if you want, but personally I don't think it adds all that much to the gaming experience. You do you though.