Manabe can't seem to keep his mouth shut. He usually blurts out whatever he's thinking, regardless of how silly, rude, or perverted it is. He even has a Did I Say That Out Loud moment the first time Kotoura scans his brain; everyone else reacts with denial or confusion. This is why Kotoura's power doesn't bother him: he manually broadcasts most of his thoughts anyway, and has no interest in keeping secrets (unlike everyone she knew in childhood).
This trait was eventually lampshaded by Haruka in episode 12, as the reason why she loves him
Another important thing is because being a Living Lie Detector was so soul-crushing to Haruka, Manabe actually gives her rare moments of emotional stability.
A minor example that might count in the moment (but is spelled out afterwards) is when Manabe, Daichi, and Yoriko bed down in a priests house, and the priest turns out to be just as much of a paranormal nut as Yoriko. Now this may seem like an unlikely coincidence, especially for a religious man, until you realize that this man lives near Haruka and was approached by her mom in the first episode in a short scene. It's likely this led to paranormal research. Of course, this is confirmed explicitly minutes later.
Why did Manabe found himself having to run his libido off episode 8? In the first glance it sounds like he was just shy, but notice that Haruka didn't know she was Brought Down to Normal and saw Manabe as thinking nothing at all. If he did anything beyond just sexual fantasies—judging from what was in his head, he could just did if he just followed his libido—his image towards Haruka will completely be ruined. God, everybody knows how would that work out...
The choice of the Ending Theme The Flower of Hope's producers. Choosing Haruka Chisuga as the singer may be obvious enough, but choosing Ai Kawashima as the composer and lyric writer takes the cake. Why? Judging from The Other Wiki's information, she can be seen as a Doom Magnet towards her parents, biological or adoptednote Outside of a Disappeared Dad, all of them died before she was 16. Biological mother died at 3, adopted father at 10, adopted mother at 16. Familiar enough? There aren't many people who can author "There isn't a lie in my tattered life/ but will truth come to me, if I imagined about it?" with experiences.
Losing the stray cat is bad enough, but Haruka's utterly horrified and crushed expression when the fat bitch tells her the cat's been sent to a shelter can have only one reason: the fat bitch killed the cat.
In the equivalent of Episode 4 in manga, when the Monk recalled how he started to understand Haruka's pain, he used a different exchange than what is shown in the anime. At that time, Haruka suspected she was sick, and the Monk of course didn't think so. Haruka then mentioned why she felt that—her mom Kumiko wants to send her to a hospital, which caused a lot of friction between the latter and Zenzou. It's not so apparent, but given the context—especially if one have watched the Downer Beginning—it's a mental ward that was in Kumiko's mind.
Detective Tsukino's situation can also be considered this as a parallel to Haruka's own situation. Had Manabe never interacted with Haruka, she may have been the one doing the murders herself.