The ending is sort of heartwarming, but not too heartwarming. [...]
That would leave room for a sequel if they get the money for one.
I'm sort of conflicted about the sequel business. The track record of such sequels is mixed. For example, I think Honey and Clover received a good sequel (although personally I hated its messaging, it was well made). Nodame Paris Hen, however, was a disaster (although Evirus liked it).