This was a neat film that had me chuckling to myself at several points throughout. Although I haven't read the novel this movie was based on, I heard that it clarified a few things that were not made explicit in the movie. I'll list the big ones here (spoilers):

[spoiler]First off, the "Aunt" in the movie is actually the main protagonist . That's why she knows so much about time leaps and talks about her senior high crush.[/spoiler]

[spoiler]The painting is so important to Chiaki because it contains the formula for time travel or is essential to the ultimate discovery of time travel.[/spoiler]

[spoiler]The career path that Makato planned to take was either art restoration, so she could preserve and protect the painting, or maybe she went into the sciences to discover the secret to time travel herself.[/spoiler]

[spoiler]The second idea seems more likely as the film tried to differentiate her from the Aunt. Instead of sitting around waiting, she would "come running."[/spoiler]

Anyways, I thoroughly enjoyed the story but I still think it could have tried to be slightly more explicit in the revelations they were trying to get the audience to perceive. The film was unfortunately designed in a way that makes things more difficult to understand if you were not already aware of the 1967 novel that started the many eventual adaptations. It's worth a look and if you're confused by the end of it, come take a look back here and you might appreciate some of the details of the film a little better.