One of the hidden events in this game that it's possible to find is the birthday celebration for Fangmei, the young girl at the Man Mo Temple. This is how you see it:

The first thing to point out is to talk to Fangmei every time you see her in Wise Men's Qr. Do this every opportunity you have. Now when Xiuying is getting you to catch the leaves to get the Wulinshu book quit and go to Pigeon Park (the big fountain in the middle of Aberdeen) and talk to Eileen, the martial artist training there.

When carrying the books to the temple library finish them all before noon. You'll have to run for most of it to make it, but when you finish you should get a cut-scene with Fangmei bringing you tea. For the next few days don't finish the book carrying task otherwise you'll get the scene again and will mess up the sequence.

After you have the Wulinshu and have decoded the paper with Guixhang, wait until the next day and go to the Man Mo Bistro in Wise Men's Qr. You should see Eileen and Fangmei together, go and talk to them. Now do the Chawan Sign at either the Man Mo Bistro or Heavenly Tea House (Green Market Qr). You'll be told to go to the Come Over Guest House where you will get a message to go to Man Mo Park (Wise Men's Qr). Go there where you will get into a battle and lose. This will trigger another cut-scene with Fangmei.

After the scene when you meet Zhang you will have a scene with Xiuying. The next day you'll have to take a detour through Lucky Charm Qr, so go there and see the cut-scene with Joy. After that scene go back to the temple library for another scene. Go to the Man Mo Bistro and you'll have to do a couple of QTEs. The combination for the first one is Down, X, and the second one is simply A.

Go to the antique shops by the gate between Wise Men's Qr and South Carmain Qr at around 2pm and find Eileen. She'll tell you Fangmei's birthday. Now go to the temple to find Fangmei and follow her to a shop in Lucky Charm Qr. After the scene talk to the shopkeeper.

On March 3rd go to Xiuying's apartment where another cut-scene will occur.

Now when you reach the part when you're about to leave Hong Kong and are supposed to say goodbye to everyone, talk to Delin, Jianmin, Guixang, Master Zhoushan, and Zhangyu (you should know them if you've been paying attention through the game). After that go to Xuiying's apartment for a cut-scene. If this has all been done correctly you should get the birthday event when you leave Kowloon.