As LAGS mentioned in the previous comment, the feature has not yet been added.
If you look at the Wiki in spoilerish mode, you’ll see Masuo’s apartment mentioned, but as you know, in the current version, none of the apartment-related places are open.
The content can be found in Mayscape Apartments, the area that will be added to the next update, and LAGS has also left a small hint with the content that it will be started through Regina’s quest in that map.
He announced that the next LSH update will take place after the HTA 1.0 update, so I think we can see it at least around the end of this year.