It was more of a filler chapter, a sibling conversation during training, then a brief moment of Arata and an embarrassed Ouka, and we jump to Minami who somehow discovered the truth about Yamaguchi. Honestly, I would be more convinced if it were Shion who came to ask Yamaguchi and not Minami, because as we know Shion was the only one actively searching for the biological parents.
Well, the next chapter will certainly be intense.