Izdahl loses his temper in a stunning manner, once Armando makes a troubling request in The Architect’s Guardian, Chapter 29. Here’s a portion:
Izdahl could see that things were getting out of control. He knew that it was reasonable for him to be upset but he thought that the level of anger he was feeling was out of proportion to the circumstances. Yes, Armando’s dream worried him. Of course, he was incredibly eager to participate in the tournament. Definitely, he’d reconsider, given what Armando had told him. Naturally, he was furious that he wasn’t told this earlier. Still. The rising tide of fury was already too high. He was now changing into his second Nitelge form, his cuspids lengthening.
Kouta’s temper causes him to do something he regrets in Balance, Chapter 21. Here’s a portion:
As much as Kouta was looking forward to seeing Ryuu, he ended up being in a foul mood when he went to his lover. He had argued with Yosuke, since he’d been three weeks late in providing lyrics for several songs. His focus hadn’t been the same as usual and Yosuke had strongly reprimanded him. Kouta knew he’d been preoccupied over Ryuu’s situation with Alexis. However, he didn’t want to explain that to Yosuke. As his manager had demanded answers, Kouta had opted stubbornly to keep quiet. Unused to that amount of belligerence from Kouta, Yosuke had speculated that there was an issue involving Ryuu. After over a decade of managing Kouta, Yosuke could figure out what circumstances affected him the most. He’d told Kouta that he should stop having a private life if it was so difficult to control. Livid over the comment, Kouta had left Yosuke’s office, slamming his door.