I'm somewhat surprised at the number of people who seem to think this is a reveal that they were predestined to be together. They're no more predestined to be together than Chisaki was predestined to keep Shakuhito from sealing Kogarashi's powers and averting a yokai war.
Remember, Ryuuzen is just calculating possible futures based on what her all seeing eye can see. She can calculate what is the most likely future at present, or she can calculate a possible future with the outcome you desire. When she showed Chisaki the future with Kogarashi's powers sealed, she was showing Chisaki the most likely future. What she's showing the girls now, and showed Yuuna on her death bed were possible futures with outcomes favorable to them. The difference is that unlike Karura whose path to her future with Kogarashi involves someone summoning invading aliens, the dying Yuuna's path to a future meeting with Kogarashi just involved her becoming a ghost haunting the Yuragi Inn.
Given that the future Yuuna saw on her deathbed was only a possible future, it's likely it doesn't take into account things like the other girls competing for Kogarashi. Indeed, given that we only see Yuuna and Kogarashi in the bits of the future we were shown, it's possible that that future Yuuna saw involved no competition from other girls, but had requirements to reach that weren't fulfilled. For example if Nonko hadn't moved to Yuragi Inn, Sagiri would have never been sent there to monitor her. Averting a whole chain of events of Sagiri and Hibari meeting Kogarashi and falling for him.
So yeah. This isn't something fated from what we've been shown. It's just an application of looking at a possible future, and taking steps to make it a reality. It's not even clear that the future Yuuna was shown on her deathbed is the one we've had so far.