Blue Lug have 3 shop branches in Tokyo. Hatagaya the HQ, Kamiuma the nerdiest shop of all thee and Yoyogi Park which is the cleanest and the busiest of all the stores. Each shops have their local park. They unofficially made some souvenir caps for those parks, just for the fun of it.
Compared to the other local parks of the other two Blue Lug stores, this park is by far the most depressing park to be honest. It's built under a hill so it's dark, has a pathetic water fountain that the water is always kinda cloudy and disgusting and the park itself is really small.
Oh, and the amount of mosquitos in this spot is awful, hence this design.
Photo Credit: Blue Lug