If you're looking for manga similar to Cyborg 009 VS Devilman: Breakdown, you might like these titles.
It's been 6 months since the L5 Campaign, the conflict that pitted humanity vs aliens with the whole earth sphere at stake; even thought at that time humanity joined forces as a whole and fought valiantly for it's survival, now that the true threat is gone the remains from old conflicts that have kept discord among people from even before the aliens arrived have started to resurface and thus the fight is far from over....
Tatsumiya Island is a small, idyllic haven for those lucky enough to call it home...until a surprise attack by a savage enemy shakes the water-locked paradise to its core. With Festum on the warpath, it's up to the island's dedicated inhabitants to pilot powerful Fafners and fight back! Before the gun smoke clears, illusions will be shattered and lifelong friendships will be stretched to their limits. Will this peaceful island survive the chaos of all-out war? Fafner- Dead Aggressor is a full-throttle fight in the name of defending peace and defeating evil! When a group of friends gears up to take on vicious Festum attackers, there's no telling who will become a hero...and who will be sacrificed to the ravages of battle. Life as they know it is on the line, and these brand-new soldiers learn to trust their instincts (and one another) in order to man their Fafners with fearless skill. Man and machine unite to take down all invaders...and save the homeland!
One night right before summer vacation, Daichi Manatsu, a second-year in high school, sees a weird round rainbow floating in the sky above Tanegashima and ventures there alone. He has seen this rainbow before. With the memories of his father's mysterious death and an encounter of a mysterious boy and girl, Daiji arrives on the island while the alarm of a building labeled "Earth Engine" is going off. Someone asks him if he's a captain, just as robotic intruders from Uranus called "Kiltgang" arrive. The battle around the shining stars is about to begin.
Set in the near-future, a little-understood form of matter known as "Mile One" allows a powerful and influential Japanese family, the Gowa, to produce a bipedal weapon which they refer to as a Tactical Armor (TA). At this time, a war breaks out between the US and the fictional Middle East country of Belgistan, much like the Gulf War. When US military forces attempt to seize the capital, they are systematically wiped out by what appear to be rival TAs. The Gowa Family seizes this opportunity to demonstrate their weapon system, and civilian pilot Yuushiro Gowa and the military squad to which he is attached are deployed to Belgistan. There, he meets rival TA pilot Miharu, with whom he seems to share a deep spiritual bond.
Based on the Toei anime version of the 70's, crossover with Devilman, Mazinger Z, Great Mazinger, Grendizer, Cutie Honey
Duke Fleed is the sole survivor of an attack on the Vegan Empire; he defends his second home, the Earth, from the Vegan attack, together with the giant robot Grendizer.
Saiga Junki is a normal high school boy who tends to be a little apathetic in general but who does manage to get better than average grades. When his archaeologist father, who went to investigate some ruins, is found dead, the family travels to the excavation site where Junki meets a mysterious stranger who gives him a ‘gift’: an ancient artifact that his father left for him…