In the last episode of the anime of Kimetsu no Yaiba, Tanjiro says to himself that he needs to combine both breathings (water breathing and dance of the fire god breathing) to achieve better results (such as lasting longer and being faster), and that's what demon slayers did all the time, they adapted old breathings to their styles, creating new breathings.
In this case, when Tanjiro uses both breathings, we see flames and water flowing around his swings with the sword. What does this mean?
Did he create a new breathing, or is he just quickly switching between the 2 breathings?