The artist titled this Wedding - Sona Ahri so I'm leaving it tagged with wedding dress even though their dresses don't look like typical wedding dresses. Feel free to modify tags as necessary.
The commentary is "After finished commission, I draw Ahri wedding with her" so it very likely depicts a marital union of Ahri and Sona.
There is a pixiv manga reupload by the artist that fixes Sona's breast size (smaller) in all 6 images. View it here. I don't find it worth reuploading, but I bet someone else will upload it.