Ten years after a cataclysm nearly destroyed all life on the planet, magic prodigy Lag Logline is entrusted with the title of "sage" and given the task of preventing the world's destruction one thousand years from now. However when he awakens from his time freezing spell the world he finds is nothing like he remembers. Upon meeting a swordswoman named Clau, Lag finds out that this world one thousand years in the future doesn't know what magic is. After having his own magic mistaken for swordsmanship, Lag enrolls in the Imperial Sword Academy in order to unravel the mysteries of the world around him and fulfill his promise to save humanity.

A romantic comedy given by the sword of the evil!! The secret of Hikari, a student council president who has excellent grades. That cannot be changed because of their illness. The hero who knew it had to help her change!

15 years ago, a mysterious "Ray Ring" of light appeared, encircling the world, thereafter on occasion dropping mysterious objects called RUMs to the ground, which cause small localized disaster areas. The objects are predicted and the disasters contained, so the RUMs are largely ignored by the public.

Under this incredible backdrop, the ordinary Seita Tooki has just been confessed to by his lifelong enemy, Awayuki Kujou. Before he can give her a proper reply, a RUM unexpectedly descends, surveys the situation, and proceeds to kill him, as well as the entire city nearby as collateral damage. As it turns out, the Ray Ring above is apparently home to 7 billion "Grim Reapers", nearly all of whom seek to deny their newfound love.

From MangaHelpers:
Second Lieutenant Mononobe Yuu has been sent to Midgard, to attend the all-girl's school where his sister Mitsuki is the student council president. The school is specifically for people who have "D" powers, who are needed to fight dragons, and both Mitsuki and Yuu fit the criteria. On his arrival, he meets and befriends another classmate named Iris Freya, who is having difficulties with her "D"-related schoolwork. They will do their best to succeed in this dangerous world.