I didn't realize this, but I read a comment on reddit that explains what happened with Ogata; what he's seeing behind him is the ghost of his half-brother, Yuusaku. Asirpa reminds Ogata of him because they're both pure, having never killed anyone.
I've started to think that Ogata is allied with the Central government, ever since the reveal that Kikuda is. This kind of throws a wrench in that theory, since Central's plan is to let Tsurumi find the gold, and then eliminate him, but knowing Ogata, he'd definitely betray his bosses' plans just to spite everybody else, so it's not out of the question that he's working with Central. That, or he really is just doing whatever he wants and messing with everyone.
Also, I've just thought of this now, but doesn't the Republic of Ezo plan also side with Kiroranke's goal? It seems like Hijikata could've told Kiroranke that his plan would provide a country for the Russian partisans and they would be on the same side. I guess Kiroranke wanted to carve out a home for his people in Russia instead, but I don't see why he would care where the land was.