If you're looking for manga similar to Leviathan: The Last Defense, you might like these titles.
On Pomello Island, a wayward genius named Enji has finally decoded the Encyclopedia of Summoning and with it the knowledge to summon and control the dreaded Yellow Dragon. The power of the Yellow Dragon is to command all the animals of the world; and with it Enji plans to at last gain fame, respect, and the affections of his beloved Moegi-san. The conditions are right, the huge egg opens, and out walks... a little girl? Enji's plans for world domination and winning the love of Moegi-san just fell apart. Or have they...
What would you do if you had a drop-dead gorgeous Mom? Not only that... but one that’s extremely overprotective, extremely kind, and gets lonely extremely easily? And to top it all off, she’s also 'The Strongest Demonic Dragon Who Has Even Eaten a God?!' The curtain boldly opens on the ultimate and extraordinary “mother-son” fantasy of Ryuuji, the young man who dreams of being an adventurer, and his overprotective mother, the demonic dragon Karma Abyss!!
Features LGD shenanigans with Ch'en and Swire fighting, Silverash siblings, Penguin Logistics doing what they do best - everyday troubles and day-to-day life at Rhodes Island!