Oh ,we are at the usual trope "We were almost close to a happy resolution for everyone, so let's suddenly do something apparently despicable and out of character to reset the drama once again".
It's not really matter, but does she threaten him by sex video? Oh my, how scary! How can you blackmail someone with no wife, girlfriend or some kind of fragile social status using such recording? He should be proud of this tape if anything.
I must congratulate the author you did it you actually managed to keep your story together not only did you do that you also managed to finish the girlfriend plot before 50 chapters good job and congratulations long Live this Magna
Any sane person would tell them all to fuck off and cut them out of their lives, except Kido's original buddy from the beginning. If that guy turns out to betray Kido too, well...