Share House with Terminator

The year is 20xx. Machine and Man have been waging a war with no end in sight. Amidst all the violence, the machine army decided the leader of humanity, Ootani Akira, ought to be erased from existence, so they send an assassin back in time to eliminate him! However, the Ootani Akira of the past was nothing but an incompetent human being, and what's more... every other character is even more incompetent?! (Source: Kodansha, translated)