He keeps listening to Hattori. I keep saying the guy is a bad source of advice for long-term relationships, since all evidence points to him never having a serious one in his life. His advice is worthless for someone trying to have a serious, committed, long-term relationship like Yamato. And the guy has convinced himself he needs to keep pushing, now, like an idiot.
From my perspective, Yamato is in uncharted territory for Hattori, even if his relationship with Suzuka hasn't gained a physical, sexual aspect.
In addition... I feel like his approach lacked any sense of propriety or tact. If there's one thing Hattori was right about, it's the idea of setting the mood, and he was doing a piss-poor job of setting and reading the mood. At the very least, I feel like he should be focusing on the kisses a bit more.
Lastly... why are they still struggling with this whole communication thing? They still need to communicate- it's the most important part of a relationship. Why couldn't he discuss things with her, including mention the fact that Hattori put shit in his head? Would that have been excessive? Anyway, I feel like every time he gets advice from Hattori, it just makes things worse, and he should have noticed that by now.