It's good that Casimero is just keeping his mouth shut at this fight.
Maybe he was being advised not to make too many talks and just do all the talking thru his punches in the actual fight. Akaho, on the other hand, is not giving any trash talks too and I'm sure he wasn't like that, and that may be the reason why Casimero is just silent too.
Casimero needs to do his best to win this fight. Still, a long way to go for him to be considered for a big match right now that's why every win is a must.
Not really surprised that this Ryo Akaho is also silent since their fight has been scheduled because Japanese people are known to be polite, courteous and very respectful towards other people. However, Casimero is different, this man is known to be messing with you in the head until the day of the fight. He just never stops talking about anything that sometimes he already looks like a fool, but this time is different. He is now under the radar pouring all his days in training for this fight of redemption.
I haven't check Akaho's record but probably this could be the first time that he might be facing at least a well known boxer, so he didn't know how to react. As you compare to Inoue, wherein he always respond to Casimero's taunt on social media.
Overall though, Japanese fighters are respectful towards their opponent and as long as they are going to be respected, then there are no bad mouthing. And yes, definitely, there is a issue on the language as well.
Japanese fighters do have that kind of tradition, they respect people and like what you have said, if there's no badmouthing they will not engage
they will just fight for a win as culture state that they needed to bring everything with pride.
On the other side, Casimero should learn from it and do the same, just fight and show what he got inside the ring.
Better to do it in action, not in words, proving something can be concluded after the fight!