TOKYO — President Ferdinand Marcos Jr. began his five-day official visit to Japan on Wednesday, his first trip to the East Asian country since taking office in June last year.   Marcos and his delegation arrived here at 5:35 p.m. local time on board PR 001.   The President is scheduled to meet with Japanese Prime Minister Fumio Kishida and will have an audience with Emperor Naruhito.   At least seven key agreements will be signed during the visit, which Marcos said would be “very specific” since every meeting he would have with the Japanese would have set objectives.