Saikano is fucking awesome, I've read like 3-4 volumes of the manga and thought it was great, I didn't think it was too heavy but it was great.
There was one OVA I did like, something about the last love story on the planet, where this girl goes off to fight some war in space, and the only way she can communicate with her boyfriend was text messages, but the further out she went the longer the texts took to come, eventually it would take like 20 years for a text to come.
I forget the exact details of the ending, but it was good
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