Leaving
Leaving
[Cueball looks down at a puddle on the floor and speaks to someone out-of-panel.] Cueball: Hey, while you're out, can you pick up some spray cleaner that works on cat vomit? Voice: Can do! Voice: Bye!
[Cueball extends his arm and faces the leaving person.] Cueball: ...Wait! Voice: Yes? Cueball: Uh. ...You are in my heart always. Voice: ...?
Sometimes, when people leave, I'm seized by a sudden fear that they'll die while they're out, and I'll never forget the last thing I said to them.

The caption below the frame tells us that Cueball is afraid that if someone were to die unexpectedly, then he is afraid that he will not be able to forget the last thing he said to that person. In the comic panel, Cueball has observed a mess on the floor, presumably cat vomit. He asks the second, off panel, character who is leaving to "pick up some spray cleaner that works on cat vomit." Cueball suddenly realizes that should the off-panel character die on that errand that this would be the last thing he said to them. Panicking slightly, Cueball interrupts their departure and says something more appropriate as last words - "You are in my heart always." The off-panel character is confused by this statement, not being aware of Cueball's fear.
In the title text, Cueball is realizing that if he hadn't have made this last-minute addition, and this person dies, his last memory of them might instead be that he was staring at cat vomit when he heard. This thought might in fact be the thought that prompted him to make his parting comment.
[Cueball looks down at a puddle on the floor and speaks to someone out-of-panel.] Cueball: Hey, while you're out, can you pick up some spray cleaner that works on cat vomit? Voice: Can do! Voice: Bye!
[Cueball extends his arm and faces the leaving person.] Cueball: ...Wait! Voice: Yes? Cueball: Uh. ...You are in my heart always. Voice: ...?
Sometimes, when people leave, I'm seized by a sudden fear that they'll die while they're out, and I'll never forget the last thing I said to them.
