Every year, there's a birthday comic strip for both Milk and Mocha (this one from 2021) depicting the two bears (and Matcha) celebrating together. It's always adorable.
Individual comics
Matcha's introduction starts off as rather sad, but swerves back into heartwarming when, even after he bit them and scared them away, Milk comes back anyway, carrying an umbrella to shelter themselves from the rain. This then goes into Tear Jerker territory, when Matcha clings to the box and refuses to leave. What does Milk do? Sit in the box with them, umbrella raised, shielding him from the rain until it clears.
Even though Mocha wasn't particularly keen on Matcha, they went out to find Milk after they went searching. We then cut to Matcha, sleeping happily on some towels drying off, adopted as the newest family member.