This mecha paper model is a sky warrior Susanoo, based on the anime Yamato Takeru, the paper robot was created by nononku. In the anime, all the giant alien robots are called "Demon Air War Gods" or "Dark Sky Warriors" in Japanese. These robots are bio-mechanized with their own personalities, feelings, and unique powers.
All the pilots of these fantastic machines are actually kidnapped children that were trained to be obedient, skillful, and murderous agents of their dark priestess. Though robotic in form, they are made through bio-mechanical incubation and have the ability to evolve over time to take even more powerful forms.
All "Demon Air War Gods" recharge through special bacta-like pods which repairs and recharges their energies, but because they are also living machines they can eat as well. All their internal cockpits have crystal orbs which act as an interface with their pilot and also respond to human emotions to react accordingly to the pilots feelings. In After War, when Susanoo's arm is cut off it reveals a beating body of flesh underneath that further proves that the Sky Warriors are indead alive. Susanoo is one of Sky Warriors.
Susanoo once belonged to a merciless unnamed pilot that used Susanoo's powers to destroy seven worlds. Susanoo's pilot for unexplained reasons landed upon the green planet and died there leaving his sword behind along with his remains.
Yamato would eventually stumble upon Susanoo and used its destructive powers for good, but never once realizing that inside Susanoo also lies the dark spirit of the one of eight-headed dragon. Through combat, Susanoo eventually evolved into a larger and more powerful form to defeat his enemies.
The dark dragon spirit that once resided in Susanoo left when the very energies that bound him were used to revive Yamato. In time the dark energies that resided in Susanoo were cleansed through Yamato's journey. Susanoo would eventually develop a psychic link with Yamato and respond to his every thought and intention. In the After War OVA Susanoo is once again called upon against a revived Shuranoo but because of Yamato's unwillingness to destroy Mikazuchi, Susanoo is beaten and loses an arm in the process.
Shuranoo pushes Susanoo into the Yakumo lake where it was healed by the Dragon Carrier and subsequently evolve into his 3rd form which is a red samurai-themed armor. In the end, Yamato takes Susanoo towards the sun taking Tsukiyomi and Oto with it, but Mikazuchi intevenes and takes control of Susanoo and sends Yamato and Oto back to earth as he sacrifices himself to kill Tsukiyomi and approving Yamato and Oto being together.
You can download this robot paper craft model here: Yamato Takeru - Susanoo Sky Warrior Free Papercraft Download