Japanese needs not plural form, but needs templates.
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Hi, and welcome onboard transation force!
You are quiteJapanese needs not plural form.
In this particular case, make it into Template:Tl:PLURAL:$1 (tl: is for nulling template effect on your userpage), as you see, I ignore plurals by fusing two bars "|" together.
FYI, please remember those funny looking Template:Tl:PLURAL:$1 is still required, or if delete it, the system will alart proofreaders as an error.
Cheers,