
If you're looking for manga similar to Code Geass Gaiden: Boukoku no Akito Picture Drama, you might like these titles.
Student/hacker Konami purchases a cordless phone from a door-to-door salesman and finds that it possesses the power to transcend space and time.
The time is set in the Mechatronics Era in the future. In this era, schools actually float in the Tokyo sky at around 2000–3000 meters. At home, there is freedom in movement as everyone has a flight mechanism within them which allows them to fly. Transportation is made easy as a result.
Hinata Taiyou has unrequited love for Kinoshita Hazuki which is stalked by guys from around the city, let alone the universe. In order to protect her from his fellow stalkers (Yeah, he's one of them), he will use his stalking skills.
The pudding empire's home planet only has a lifespan left of one year. Thus, they aim to invade Earth and make it their own... but first they've got to wipe out those annoying humans who are currently inhabiting the planet. Planning an invasion turns out to be much easier said than done, especially when your human-killing monsters start having problems with morale, sickness, family issues, and so forth...
COMPILER is a story about the Igarashi brothers Nachi and Toshi, and two beauties from another dimension, Compiler and Assembler. Originally sent to conquer Earth through a game of destruction and creation, Compiler and Assembler ended up deciding that living in our world is more fun than conquering it. They moved in with Nachi and Toshi. A growing relationship began to develop between Nachi and Compiler, and Toshi and Assembler, though none of them can bring themselves to admit it outright. Meanwhile, the people who sent Compiler and Assembler to conquer Earth were outraged by their apparent betrayal. They sent two assassins, Bios and Directory, to deal with the renegades and proceed with the invasion plan. And so, the misadventures begin...