Sniffer(VPN) in kcanotify is for capturing data, so it can not be used for IP bypass. By the restriction of Android system, two or more VPNs cannot be used at once. You can see detail about VPN Service in android at this official document.
It is easy to use kcanotify if you just need VPN for DMM auth:
just start kcanotify's VPN after DMM auth! (like in kancolle sound option screen)
This video (Youtube) shows an instruction for using kcanotify in above situation.
If you have any question about kcanotify, feel free to mail me. (see README)