Your opinion is noted. I'm afraid I don't get that "wound up" over fiction. Things will work out in the end - because they always do - whether positive or negative. Shingo is a fictional character and he experiences nothing, but you are experiencing a mangaka who has drawn you deeply into their characters. So, there is some good that comes out of all this "pain". Don't stress too much and just enjoy this for what it is - an incredibly well written and beautifully drawn story. Happy reading.
So true hehehe...
It is not a doujinshi, but rather the continuation of the series. It is currently ongoing, so the "bad" part we are discussing is the plot conflict of this arc. The recent updates just happen to be cliffhangers during the conflict. I'm sure things will all be resolved. Also, you must bear in mind that the "cheating" referred to here is not of the "intercourse" type. Rather, it was a "peck on the lips" that was initiated/forced on Kagami by an American director. The tension between the two MCs is related to one's insecurity and the belief that the other is "no longer interested". This conflict has come up before and been resolved well. I'm sure once this story is complete, everyone from MCs to readers will be happy.
Ignoring the most recent sequel for now. I'm just going to return to happier times when my favorite couple has super hot sex.