New Facebook Page: https://www.facebook.com/OsmaniTheOttoman/
Companionship EXP can also be obtained by occasionally visiting your Serenitea Pot and talking to Tubby to see how much they’ve accumulated. Completing Domain challenges and Ley Line Outcrop battles also increases it.
It’s important to note that only characters who are in your current party will obtain Companionship EXP. Any character not in your party won’t receive any of those benefits.
Otherwise, you can travel normally with your companions and try to get their Friendship Level to 10.
Source: https://www.distractify.com/p/how-to-increase-friendship-in-genshin-impact
New Facebook Page: https://www.facebook.com/OsmaniTheOttoman/