@anzuda
"Why i use thanks as an example, it's because the mechanism is pretty similar."
Well, i don't think that example works for 2 reasons:
1) she said I love you to Nasa himself. Your example mentions 2 different parties, we are talking about the same person here.
2) Saying I love you is different than saying thank you. It should have been harder for her to say that to Nasa when days after their marriage (while meaning it that is, and i don't think she didn't mean it that time) than a couple of months into their marriage.
"In this case, It's the sense of obligation to reproach the feeling that she hasn't give for a while, the embarrassment of not realizing it sooner, and what seems to me the feeling of not wanting to be seen as ungrateful is what made her feel that it is hard to say it even though she used to say it easily. "
I don't think the writer frames it that way at all. These reasons are actually what spurred her to get over her new found tsunderish personality and say the word in the end, not the opposite. It's like the writer forgot that she said it before, and thought this was development for her character.
I guess in these types of conversations one has to make the distinction between what is plausible for a random human (which is a lot as humans are capable of a wide range of emotions) and what is possible for a particular character and whether or not the writer put in enough work to develop that character. To justify characters acting differently in similar situations there has to be character development. I don't see any character development for tsukasa to turn her into an absolute tsundere. Sure she was always tsunerish to begin with, but in the end always came through. Seeing her struggle so much with the word and not even say it properly in the end (she said baka, classic tsun) vs how candidly she spoke her mind back then is too jarring.
" Sorry for the wall of text and if there is mistakes in what i said."
and Sorry for my own wall of text, and if i made any mistakes as well. Seriously though no need to apologize, you were very reasonable and I appreciate the conversation
.