The story sometimes has these brief side stories. It’s happened a couple times so far. I think the tie in is supposed to be “these are the effects that the MC is having on the people around him. This is why they call him selfless.”
There was the side story featuring the soldier he healed, the slave that was proud to be running her own shop, and a couple of other short side stories featuring the other slaves that regularly reappeared in the story. This one was just a bit further away from the MC than usual.
I uuh…still have no idea how all this ties in to the main story
This manga is some what slice of life, and focuses on the other characters and stories of the town the MC made. It's a good chance some of them may pop back up in the main story line.
Like Chonjira and Tolroc said, there's a ton of side stories featuring MC's slaves or people related to them. Solmetra is one of the MC's slaves. Many times we've seen glimpses of them in previous chapters till they're finally featured or mentioned later.
Mamoy who run her own woodworking shop with Nava as seen in chapter 6, the figures she carved of the MC in that chapter and main slaves are seen at the end of chapter 9 decorating the Schenker's main offices. They also appear in chapter 12, page 16 where they build the slide for the pool. Storo who was chatting and telling gossips to Mamoy in that same chapter 6 is later featured as the one that writes a newspaper and post the stories on the Schenker street notice board.
Chapter 8 we see 4 members practicing with their music instruments and later we see them being part of a band that plays during MC's wedding in ch. 10 and his brother's wedding too. Sheena, the dark skinned dog girl, marries, leaves the band and gets her food stall and deliver food to MC in chapter 12 where the subject of the slave status of children born to his slaves comes up. And Moimo, the flat chested bunny girl Sheena was dissing becomes the defacto band and later theater troupe manager.
Opika the sheep girl and Lupika the wolf girl we get a glimpse of them in chapter 8, page 8. But Opika's story is told in chapter 16 who was sold as a slave in hopes of getting her bought by MC and having her disease cured and meeting the wolf girl Lupika in her travel. The sheep girl's blessing to navigate makes her an asset in the construction crew in previous chapters and trains and works as a nurse in chapter 15 in the sports fest and in her own story chapter while the wolf girl Lupika who became the head of security was already seen often in Chapter 11 & 12 guarding MC's various construction sites.
Chapter 17 we had the story featuring the messenger trio that work with the Schenker mail service picking their food from the various Schenker food ventures like the fish and mushroom farm, Kakura the fast messenger cat girl who had the spotlight was already shown in Chapter 15 in the sport festival winning a race and we see her even before that in Chapter 9 when Jillen, one of Chikin subordinates and office workers, ask for her help.
In chapter 19 MC mentions his regular bodyguard was the tiny dog girl with a big sword, Raffi/Lafi, but she already appeared in chapter 14 in the sparring between the various adventurer slaves.
In chapter 4 we see Elaf a bunny girl in the Schenker maid cafe serving food to Chikin in her day off. It was omitted from manga, but in the WN there's a story seen from Elaf's friend POV getting treated to food at the cafe and in the sport festival we see Elaf serving beer.
Maybe it's me who can remember all sorts of characters and their names and keep track of them. But then I wonder if people can't keep track of a couple or a few dozen characters in a manga or getting confused when story switches perspective or POV, what about something even more complex than this or stuff like Game of Thrones with hundreds of characters and multiple simultaneous storylines?