Unfortunately the second half of TOxA lost this aspect. I have not yet read the manga for TOxA so this is not a preconceived bias. The second half was very hard to get through because one of my biggest pet peeves reared its ugly head. Characters suddenly acting out of character. The writing changed and became more...sentimental and oozing with flashbacks. Lastly, things became much more predictable and less mysterious and ambiguous.
When this kind of change happens, I usually drop the anime but because the first half was so well done and because the second half wasn't completely unwatchable, I continued and finished it. Usually, when the second half goes sour, the ending is what truly kills an anime for me. Luckily, I wasn't disappointed with the ending, though I was sure I would be.
If the second half hadn't suddenly become much worse, I would have rated TOxA a 9.
