If the RPG World Had Social Media..., Vol. 1 (manga)

When a fantasy world has fully functioning smartphones and internet (for some reason), it's only natural for its sixteen-year-old shut-in of a Hero to declare war via text message on the Demon Lord who has abducted the kingdom's princess. But is it natural for that Demon Lord to be an innocent teenage girl who hates conflict?!! And somehow, this hopelessly weak, level one Hero ends up texting that overly pure Demon Lord, her cheerful Demon Generals (who are all smitten with her), and a kidnapped princess who is seriously falling for her captor as he sets off on a perilous journey to meet his online cru-er, mortal enemy face-to-face!