Payday in Japan

If my payday will be a sunday, which day will i be payed?
Friday or next monday?

Really depends on the company, but usually Friday.
You should ask your employer.

Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Or ask you employer

Probably Friday, but you can ask the boss, ask another employee, or wait and find out.

It's usually Friday, because employers are not supposed to impose any disadvantage in terms of remuneration payment to their employees.

this is written in 給与規定, pay regulation. this document has to be registered to governmental labor office, 労働基準監督署.
if there is no description about payment in holidays, payment should be done on the previous weekday.

Just to add a different perspective, my experience paying people is that it is mandated that payment must be done on the working day before if a pay date falls on a weekend or holiday - say if you are being paid on 15th or 20th of the month.
Possibly also relevant is if you are being paid in arrears (ie for the previous month), or for the current month. Really depends on your employer.
But if it is unclear and you need to come to a forum to ask, you need to have better clarity about your own employment situation and contract. Don't you have your terms of employment written down? If not, you really should.