These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Angst? What Angst? — Considering how hard he was trying to get together with Shou, he took her lying to him and getting together with another man pretty well.
However, although nobody's feelings are spelled out in black and white, even to themselves, Utsumi did react negatively to Yuki's rejection, but only after Yuki expressed her desire to go into Shipper on Deck mode for Utsumi and Shou again, not taking into account Utsumi's feelings.
A later arc had Utsumi suffering due to his inability to understand why Yuki is upset at him in the first place. Then again, he was unaware that Yuki misconstrued Utsumi trying to console a crying Shou at the sports camp.
Played straight in the current mini-arc post break-up.
Tohru, at least initially, after his proper introduction into the storyline, specially after the reveal about Yuji and what he did to both Yuki and Tohru. This is later fixed by actually making him properly unsympathetic towards the end of the series when he goes full Yandere.
The Woobie — Oonuma. After finding out why she acts the way she does, you'll want to give her a hug and a cookie. Luckily, Utsumi is there to do the next best thing.
Utsumi, too. Really, the mangaka seems to be trying to make everyone into one.