YOU SAID:

there can be only one, per two

INTO JAPANESE

2 つにつき 1 つしか存在できません。

BACK INTO ENGLISH

Only one can exist in each two.

INTO JAPANESE

各 2 つに存在できるのは 1 つだけです。

BACK INTO ENGLISH

Each two can have only one.

INTO JAPANESE

各 2 つは 1 つだけ持つことができます。

BACK INTO ENGLISH

Each two can have only one.