FNF vs W.D Gaster

If you have played Undertale, you know how dangerous its characters are. These are monsters that can act with no mercy if they see anybody coming their way. One of them, Gaster, sneaked into the FNF musical world. How can Boyfriend stay safe and get rid of him? It can be done in the same way he defeated all his previous opponents – he should challenge him to a musical duel. It will not be an easy fight, but if you focus on the rhythm and follow all music beats, Gaster will be defeated.