Da being so aware and concerned for the couple is actually quite sweet. The tax evasion comment, while derisive at face value, is implicitly confirming that this Japan doesn't just allow the 'partnership unions' (as I initially assumed back in Ch.1, as that'd be a parallel of IRL) but properly recognizes gay marriage, along with the couple's benefits that entails. Gotta appreciate the small wins. I do hope there's not drama incoming, I'm quite enjoying the meandering slice of life as they learn more of each other and grow closer.