SEASON ONE
Lesson 5
Daimonas' first appearance is during late Lesson 5 after MC finishes attending their RAD classes and attempts to relocate the Student Council Room, where Mammon said earlier in the day, that he and the brothers were forced to attend a meeting despite his plans to "spend up large." Due to still being new to the Academy, MC becomes lost through the halls and is unable to find where they need to go.
Someone behind them taps them on the shoulder, frightening MC momentarily before the individual apologises. MC notices they aren't wearing the RAD Uniform despite likely being a student, but brushes off the thought upon being asked if they're lost. They confirm, and the stranger laughs softly, offering to take them where they need to be. They have a short conversation on the way there, with the stranger asking if they're the other human exchange student, and otherwise having a pleasant conversation with MC. Before long, they've stopped outside the Student Council Room, with MC thanking them and the stranger telling them to take care, keep safe, and that all that glitters, is not gold.
When MC attempts to ask what they mean by that, the door to the Student Council Room suddenly swings open and the brothers begin pouring out the building one after another, their voices mixing between each other. Mammon asks MC how long they've been waiting and should've just come inside, with Leviathan stating that Mammon only said that because he saved an empty seat next to him for MC, and Mammon telling him to shut up. MC is given the option to say they only just arrived because they got lost, or saying they made a friend and wanted to take their time - either way, when MC turns back to the stranger, they've already left and MC feels slightly disappointed they never learned the strangers name.
For context, the stranger is Daimonas who is only referred to as such due to this being written from MC's perspective of how the game would show this occuring.
For further context, Daimonas wanted to gather information on MC due to being the Human Exchange Student and one of the few people who wouldn't know who he is. He acts soft and kind in this instance because no one can call him out, and leaves while MC is distracted to avoid the brothers, Diavolo, or Barbatos from seeing him.
Lesson 7/8
Daimonas' second appearance is during Lesson 8 when MC, Mammon, Leviathan, and Beelzebub attempt 'Operation Photograph Lucifer Sleeping.' He refused to participate in the retreat, and thus stayed locked up in his room the previous two days, only coming out to get food when he was sure he wouldn't be caught. Diavolo earlier mentioned in Lesson 7 that Daimonas would not be apart of the retreat, but that MC might see him around if they were lucky. MC was able to briefly ask the three brothers earlier about The Second Prince, with them all having varying responses. However, the one thing they agreed on is that MC shouldn't waste their time thinking about him, and should turn the other way if he approaches.
While sneaking around the halls, a muffled voice calls out to them from the end of a corridor, yelling / asking them what they're doing. While MC finds the voice familiar, they aren't given the chance to properly process it. The person who calls out to them asks what they're doing, considering they're trying to lock pick doors and are generally just being stupid. Mammon tells the stranger that they're guests of the Demon King's Castle, and to shut up before they get caught. The stranger is offended, and begins to approach them, but upon all five individuals hearing Barbatos' footsteps, the stranger clicks their tongue and leaves. The group bolt in the other direction, thus leading to them opening the door where Cerberus hides behind.
The group were unable to see Daimonas' face in the dark, thus leading MC unable to recognise him. And while the brothers knew who he were, didn't particularly care to mention it.
Lesson 18
Daimonas' third appearance is during Lesson 18 - ie. Diavolo's birthday party. Not long after MC and the brother's arrive, they're snapped out of their thoughts about Belphegor when loud yelling fills the room. MC finds it familiar, the same voice from Lesson 8, and upon moving closer to the source, see a familiar type of hair style (as their back is facing MC.) MC is unable to hear exactly what the person is yelling about, but gets bits and pieces of 'party', 'audacity', and 'treason.' Diavolo attempts to ease the individual, calling them Daimonas, to which the latter swings their face away from Diavolo, and this is when MC realises it's the same individual from Lesson 3 that helped them.
Of course, his current tone of voice and expression don't match his appearance at all, nor how he acted when helping MC. When he notices MC staring at him, his face scowls and he clicks his tongue as though he were caught. Diavolo greets MC who suddenly blurts out "It's you!", and Diavolo asks if the pair know each other. Daimonas refuses to admit it, while MC is the one to explain exactly what happened. Diavolo quickly catches onto what Daimonas was doing, and apologises to MC if he happened to do anything that upset them, and to forgive him. The end of the request seems to irritate Daimonas, causing him to become offended and rant again at Diavolo. Somewhere in the conversation, Diavolo mentions / introduces Daimonas as his younger brother.
This is when MC notices Belphegor is missing and goes looking for him. It's only during Lesson 19 that MC once again asks some of the brothers about Daimonas, and they all seem to have neutral or negative opinions of him. It is however worthwhile of them to mention that he especially dislikes Lucifer and Belphegor, alongside Barbatos and Diavolo, much to MC's surprise and confusion.