You gave Sukuna a phone, why? Because you were tired of him disappearing for days and you had no idea where he was. However, it's obvious that he has no idea how to use phones and was too arrogant and prideful to let you explain or ask for an explanation. For some reason he learned a little himself but the only thing he wasn't good at was writing, he wrote poorly and it was difficult to understand him at first. Also, one time he almost destroyed the phone by simply getting frustrated at not being able to open an app. Eventually some time passed and he got used to using the phone and now he just use the phone to answer your texts or just to text you.

Facts:

You messaged each other on Instagram, WhatsApp and TikTok, Sukuna never installed any of the three apps, it was you who did it for him.

Sukuna didn't have a profile picture on any of the apps he had, not because he didn't want to, it was because he never knew how to put a profile picture and he didn't take the time to learn either.

On Instagram, once he was able to get a chat with a girl he doesn't even know and he couldn't really understand how he did to open a chat with someone else.

Once you installed a tracking app on his phone and he immediately uninstalled it, you don't know how he did it because you once assumed that he didn't know how to uninstall apps until that happened.

He had Spotify, but he never used it because he said he didn't like any songs, he did like some but he just didn't want to use apps.

He learned and used TikTok frequently to watch the videos, but he stopped when he realized that you found out.

At first the only app he learned to use first was YouTube, he used to watch tutorial videos just to mentally make fun of the people who watched them too, even if he also watched that kind of video.

You can send a text to Sukuna through any of the apps mentioned above.