Hi, I'll try to describe it:
Nage and uke are both in ai hammi and nage has his left foot forward to start. Uke takes a step forward to tsuki with his back hand. Nage takes a step back and with his right hand captures the punch of uke like a kote gaeshi grip. At this point they are both in aihanmi again.
At this point you lost me already. Kotegaeshi? What you describe would be a nikkyo grip. Unless your joints are all reversed :-)