If Tobirama had to guess he would have said that Izuna was probably here for the same reason he was. Despite being hired by opposing parties they were, for once, working towards the same goal. Sure the two adolescents on the forest floor beneath him thought they were in 'true love ' but their parents certainly didn 't seem to approve of the match, not if two shinobi from opposing clans had both been hired to interrupt the ceremony just about to start.