Oikomi is a training method in order to increase your speed, balance and strength.
Motodachi runs back fast so that kakarite can keep striking.
However, it is an advanced method so it is not recommended for beginners.
That is because it is easy for you to lose a coordination of the whole movements especially fumikomi and strike coordination.
Some points that I want you to pay attention to when exercising this method.
Motodachi literally runs back. Hence, not only motodachi but also kakarite must be careful.
As always said, a valid strike means you have ki-ken-tai-icchi and also strike a datotsu-bui with monouchi of shinai. So please make sure that every single strike should be valid.
If you have a long dojo such as a basketball court, you may want to give it a try.
Again, make sure that there are no obstacles behind motodachi.