Jenny/Manila

This is with regards to our Company Superintendent who is schedule to attend and supervise the repair/drydock of one of our manned vessel at Qingdao, China.
He is a Japanese nationality, Holding a valid Japanese Passport and I think Japanese have a 15 days free visa going to China.

But if he will stay more than 15 days, what will be the requirements? Can we apply him here at Chinese Embassy Manila? Does he need the Original invitation Letter?