Mashuu concept of "love" isn't fully developed, what he believes right now is more of a parental love than a romantic. Satoko filled in the gap of missing mother during Motoki overworking time.
It's pretty clear Ogata switched to being a supportive to Mashuu goal, into falling in love with him, christmas present was the start of it.
Well I root for them, it will be hard with how conflicted Mashuu is right now, it will be difficult for him to notice as he helds Satoko way above any other right now.