Little Taku has a track record for acting first and thinking about the consequences later, so Secchan is understandably worried. But he doesn't like to promise things he knows he won't be able to keep, even if it means risking that Secchan might start crying again.

This is the first time we hear of PACT, the "Port Astraea Combat Team" which handles cases that are too dangerous for the police to handle. Most big cities have a Combat Team, but unfortunately, none of the other abbreviations sound as nice as this one ;;;

Setsuko: "Promise that you'll never go to a dangerous place like that!"
Taku: "Huh...!?"
Setsuko: "You're always so reckless! What if you run into some evil guy too?"

But Taku is confident that he'll be fine.

Taku: "Come on, I wouldn't let myself get killed that easily! I'd fight back and win!"
Setsuko: "...does that mean you're not going to promise?"
Taku: "I don't want to make a promise I can't keep! You know that I want to become a member of PACT, like dad! But that also means that I'll have to do some risky stuff from time to time! Or do you expect me to chicken out when things get serious, just because it might be dangerous?"