He doesn't, he's a terribly written character. He's ranking with the Kamen Rider Ghost characters at this point in terms of awfulness.

It makes sense for this development to happen to him, and it's a delicious case of irony too.

And it happened out of simple writer's convenience. There was so need for him to betray Emu to begin with, but because Chronos was fresh and new, Dan and Emu couldn't beat him that quickly. So, they had to have sad boyfriend step in. And don't even get me started on the Kiriya crap, thanks for ruining a character I liked, Toei.

Just like with Drive, Ex-Aid is stumbling at the finish line it seems. Shame too. I was enjoying the series.

But Hiiro's motivation early on was killing Graphite for Saki's death, and he doesn't feel satisfied as it didn't bring her back, now that he knows she CAN be brought back, he's willing to do anything for it. And I dunno about Kiriya, eh, I guess it's just a matter of opinion then

And Emu expressed he would have helped Hiiro achieve that. So, with that, and the plan that was cooked up early on...Hiiro didn't need to betray his bro. :rolleyes

Yeah....I think if I become Masamune, I will kill Paradox.....

He also has other strange decision...why he decide to not kill Emu and other Riders when he was able to stop time? If Cronus kill Emu and other Riders, his plan will be successfully.

In episode 36, Masamune use freeze time again and steal Hyper Muteki Gashat from Kuroto. He just steal Hyper Muteki Gashat without kill other Riders. Or, if Masamune didn't want to kill other Riders, he just need to steal other Gashats when he use freeze time ability.

One thing to remember, as much as Masamune hates Emu and the others, they are still valuable products for Kamen Rider Chronicle. He, of course, won't take too much effort and action unless they really do something to oppose him. Basically, 90% of his screen time, Masamune only fights because the other side provokes him first. Lovrica is the worst offender since, yeah, he got Game Over-ed due to his arrogance. Also, plot armor, you know (Insert Thug Life meme here).

While it pains me to say that Hiiro is a rather bad written character, I must agree with Zilla on this. It's plainly stupid for Hiiro to just betray Emu and the others after having such WELL PLANNED plan with (Shin) Kuroto Dan. It's one of the thing that makes Ex-Aid is so confusing and too dramatic in several ways. I get that the writer needs more drama and have Cronus to be a much bigger threat but, meh, the way they executed it just weird.

However, I do justify this case to several extents. Call my words to be a paradox, but it's not that Hiiro's betrayal is good or bad written. First of all, Cronus has the Proto Gashats. He might have moved the deceased people data from the Gashats to somewhere else as what shown in this episode too. This kinda makes Hiiro's betrayal much more sense. Masamune could easily delete Saki's data pretty much anytime.

Another point is Hiiro's own character. I have analysis Hiiro's character for several times and I assumes that Hiiro is your basically typical self-loathing characters. He puts a strong front in front of the others but he doesn't open up his own feelings too much to them either. This reminds me the fact that they introduces Hiiro as a tsundere which fits his whole characterization. He always acts to blame the others but he actually blames himself much more than he blames Taiga or Graphite. The whole reason of Hiiro's betrayal is because he can't be honest with his own feelings and because of that, he enacts a rather selfish action. Just go watch ep 34, it's particularly written Hiiro's whole character there. After watching that, I couldn't blame for Hiiro to make a betrayal, as what Taiga said too.

I have to say, this is probably the first time the MOTWs are more or less regarded as a curiosity by most people rather than you know, monsters. I mean, just look at how people just pictures and selfies of Kaiden! I mean it makes sense because Masamune goes out of his way to defang them to increase sales, but it's rather funny nonetheless.

Also, Hiiro joined up with Cronus simply because the whole 'Saki in Proto Drago Knight Hunter Z' is and has always been a hostage situation. Hell, this has been the case for everyone in the Proto Gashats after all. It's literally the only reason why Genm Corp is still running in the first place. It also makes Proto Drago Knight Hunter Z ever more important to Masamune since that's the only leverage he has left. If he loses it, there isn't much he really can do against the Ministry of Health freezing all of Genm Corp's assets and ruining him.

Cronus needs to stop with these ultimatums. I can't wait for them to finally defeat the guy. I really hope tet can save Taiga next week. This episode was too sad.

Except that taking away Cronus' ability to transform wouldn't have saved Saki. Keep in mind, within the logic of the show, the Ministry of Health and the authorities can't work out a solid case against Masamune at this point. He could have easily escaped and erased Saki's data out of spite once the battle was over, and he likely made Hiro aware of that. Hiro saw an opportunity to save his girlfriend and literally had no other option other than to trust Cronus if he wanted her back.

As a side note, it's possible that someone inside the Ministry is corrupt and allowing all of this to happen. I guess time will tell.