My quick initial thoughts....
Yachi vs Gustavo:
Yachi is most definitely Japan MMA's next biggest star, representing the Krazy Bee gym which is pretty much the only MMA gym in Japan with any sort of name recognition thanks to Kid Yamamoto and Horiguchi previously. He's a perfect 5-0 in Rizin and used to be the PXC champ (I believe at 145? He currently fights at LW. a few years although he lost that belt to Alexander "The Great" Volkanovski. It was believed he would get a call-up to the UFC if he won that fight.
Like most Krazy Bee products he's a very good athlete. He's got a pretty well-rounded aggressive style and has finished 4 of his 5 Rizin wins, via 3KO/TKOs and 1 Sub. The lone sub win was against Takanori Gomi right after he got dropped in the 1st round but showed good composure to tie up a triangle on the ground. He then had an entertaining back-and-forth brawl with ultra-aggro ex-UFCer Diego Nunes in which he won a split decision. He does tend to get sucked into brawls, like in his fight against Gomi who, let's be honest, only has that one path to success nowadays.
Let's make no mistake here. Rizin has been feeding their poster boy somewhat over-the-hill veterans with name value (Kitaoka, Gomi, Nunes) up until now. So it's pretty odd that his next opponent is a 22 year-old Brazilian I've never heard about with a 8-0 record and who's actually finished every single one of his opponents.
Strange matchmaking aside, Yachi has faced much better competition and should take this handily. Gustavo's record looks pretty shiny on the outside but a look inside shows pretty low level wins imo.