This is a prequel-sequel that leaves off from the cliffhanger at the end of season 2, where Lu Guang travels back in time to save Cheng Xiaoshi's life. It uses Butterfly-Effect time travel logic to send the boys off to Bridon (London) to uncover Cheng Ciaoshi's family secrets.
There's a lot of cute character moments and interesting plot twosts that make the forst 5 episodes engaging, but my main problem is this:
It's an "arc" that resolves nothing. Previous Link Click seasons has cliffhanger finale episodes but they told a self contained story. This does not. The Final Episode resolved itself through a shitton of Deus Ex Machina - characters having abilities they had not previously been shown to have etc. Without explanation, foreshadowing or buildup. It's meant to be cool and thicken the plot, but it just feels cheap. Like a pitch for the next season (which will be the official 24-ep 3rd Season).
This is a half-season labelled as a side story, but even that inplies it tells a self contained story. It's a very entertaining side story mind you, but don't go in looking any kind of closure on anything, is all.
Oh and as ever, the backgrounds and IP/ED are brill. Thanks LAN Studio.