This is great! To all who think this is going toward NTR, I ask you think carefully about who they are as characters and the meaningful bond they have. Neither of them would give the other up. There is plenty of evidence already that they have deep feelings for each other. This is not some hentai where characters turn on a dime because some other man or woman is better at sex. These two characters truly care for each other. The closest I could see is that Yukino finds a book where the woman shares the man with another, and even IF that happens, we are likely going to see her true feelings come out and stop the play because she wants home to herself. Give the story a chance and don’t fret over NTR.