Apparently there are a lot of musical references within the series, the ones I've been able to find so far are these:
Yousui's first lines in the series (ch.7) are the opening lines of the song "Yume no Naka e" (Into a Dream) by Yousui Inoue, and fake Chanyu's rambling after getting beaten by butcher "How about dancing with me instead" (ch.9) is also from the same song
And Grandpa Masa talking to himself (ch.2) - "One More Time, One More Chance" by Masayoshi Yamazaki
Also this is the first time Major's right eye has been shown since chapter 1 and it looks identical to the eyes of the robots, I wonder if there's any deeper meaning?