Related, Connected
This gate of horns will take you to heaven. These horns are related and connected to heaven in some way.
Perhaps they are related to heaven because the devil has horns? Perhaps they are connected to heaven because these are the horns of heaven's enemies? The real reason they're connected will be revealed in the reading mnemonic.
かん
かか, せき
None
They are related and connected to heaven because these are the horns that Genghis Khan (かん) made from his enemies. God said he could come into heaven if he made a gate of horns, so that's what he did.
Imagine Genghis Khan taking horns off his enemies, and making a gate to heaven. The horn gate is connected to both heaven and Genghis Khan in that way.