The chapter 186 was fully focused on Yoriichi’s past life. We can expect the same for chapter 187 as the flashback hasn’t ended.
In Kimetsu No Yaiba Chapter 187 we will see a head to head battle between the strongest demon slayer Yoriichi and the Muzan. As mentioned in previous chapter Yoriichi will bring Muzan on the verge of death with original breathing technique, but Muzan will somehow manage to escape.
In next chapter, Tanjiro will also see Yoriichi meeting his father after the battle. Yoriichu may tell Tanjiro’s father something about the final form of his technique.
We will publish more details regarding Kimetsu No Yaiba Chapter 187 spoilers later.