Few things I got from a quick look.
Spoiler for Vol 20:
-Those two guys from GAA during the Yokohama Disturbance arc, Chen Xiangshan and Lu Gonghu, are back.
-Honoka was attacking Tatsuya using her ‘biggest weapon’.
-Tatsuya gave Miyuki a necklace for her birthday. “A ring is…..eventually, in the near future. For now, put up with this necklace.”
-As shown in one of the pics, Miyuki tried to kiss Tatsuya. She was very close like one thin paper away but changed her mind and then ran out of the room with her face completely red as shown in bottom panel of the pic.
-The next arc is called “動乱の序章 (Prologue of an Upheaval)”. Most likely it will be another one volume arc.