Tbh, since the moment Tamahiko grabbed that knife im lost...
This turn of events were awfully dark. Even with all that happened before there was still a certain balance. He making that act to force Yuzu decision and his sister killing Tamaki were really necessary for the plot continuation? Ngl, i wont be able to look at Tamahiko the same way. I get the sentiment of doing whatever is necessary but theres some lines that shouldnt be crossed. He just proved to really be a Shima. If later he dont at least regret and apologize to Yuzu it'll kind of ruin the story for me a bit.