After Malleus’ overblot Ortho checks on Idia first out of everyone, and when Silver and Sebek are crushing Idia between them it is Ortho who asks them to give him space.
We learn in Book 7 that despite how Ortho has had his own room (with roommates) since the end of Book 6, his maintenance station is still set up in Idia’s room.
Ortho’s father cautions him about making contact with Idia within Idia’s dream world, as there is a chance that Idia would reject him: “Your maintenance station was gone from his room. Surely you can put together what that signifies. This could be deeply unpleasant for you.”
The Director shares his plan of reaching out to “a professional with a PhD in psychology” to try and avoid as much confusion as possible, but Ortho says he will be fine as Idia will most likely greet him with, “A handsome young humanoid is asking me for help from inside my computer?! I’ve read literally 500 million light novels with this exact premise! Is it finally time for me to be the chosen one?!”
Ortho is proven correct.
Ortho appears in Idia’s dream in-person in order to save him, triggering a paradox as his very existence compromises Idia’s world. Ortho swears to do whatever it takes to save him.
During his Master Chef class Ortho decides to use his Cooking Gear to help improve Idia’s diet.
Ortho buys apple-core-flavored candy and a postcard for Idia at Playfulland, and in Clock Town he buys potato chips that can only be bought locally for Idia to eat while gaming.
Ortho will often mention Idia in conversation: when discussing detail-oriented people Epel suggests that performing delicate work might make someone have a delicate personality as well and Ortho comments, “My brother is a wiz with technology…but he’s not like that at all.”
He also quotes Idia during the Rabbit Run race, saying, “As my brother would say, the dungeon’s not really beat until you’ve sprung all the traps,” and says that he cannot wait to tell Idia about the experience.
Ortho says that it is difficult for him to make things from scratch, so he really respects people who are able to do so, and especially Idia.