The way I understand is they didn't give rachel to him (although Ogata talks as if he didn't want her) and he wants to make Miu change sides and might use one of Ogatas disciples as a bad guy to achieve that.
In the previous chapters nathan said that sicaldo lost interest in raising a disciple, but in this he clearly says:
me\[aim]\if let do\\silat[object]\could make master\[aim],\\that's a pity[emotion]\\
if they left it to me, I could make her master silat, that's a pity\\
So he regrets that he could not raise Rachel as disciple, in other words he was forced to leave Rachel alone
So they are targeting Miu. Perhaps they would use her father to lure her. Anyway that is an interesting development. I wonder how it will be related to Sakaki fight.
Well he talks about a kuremisaigo but he never does an explicit reference to miu's name.