@Rafa:
Hi everybody!!
Reading the official page (in English), there is a ticket for Attractions and another for Live and Attractions. The One Piece 20th Anniversary Exposition not appears in Attractions section; it appears in Event section. My doubt is if I need the complete ticket or with the Attractions Ticket is enought (I will go with friends that not are One Piece fans, maybe it's to much for them).
The Attraction ticket should be enough for the exhibit. The Live Attraction has a schedule( it's own mini-theater area) and fun to watch. The exhibit is neat and I enjoyed seeing original panels. This is the second part of the exhibit focusing on battle so a lot of it are artwork of finishing blows. Have fun!!! I highly recommend One Piece fans visiting Japan to drop by Tokyo One Piece Tower since it has a bit of everything (live shows, merch, mugiwara store, cafe/restaurant)