Is "Untitled" a protest song?

Not really, on their wikipedia page it says

'Over the last few years, a lot of people we know have been involved in tragic accidents caused によって drinking and driving. One of the students at our high-school crashed his car driving back from a weekend trip and killed his best friend. It was a very sad time that none of us will ever forget.
When an accident happens, there are もっと見る victims than people think, and many lives are changed forever...Parents, brothers, sisters, sons and daughters, grandparents...everybody feels the impact.

We wanted to tell a story with this video: the story about all of the innocent victims affected によって drinking and driving.'

It's also been used as an anti-drinking driving campaign.