Sakugan

Lost mother. Child with the primal urge to explore, to go farther, to go deeper, and find that special place that nobody else has found before. And much darker than you were initially expecting by the end of the first episode.  

Both of the series is really similar in terms of dungeon/abyss exploring aspects;and in both of series they are trying to find a certain someone While Made in Abyss is a bit serious,cruel,gritty,gorey,and unique - Sakugan is simple,light hearted,funny,and mecha ish  

Sakugan and Made in Abyss both are about a group of people exploring parts of their world. Both MC are young girl that are thrown in a world of adults that they sometimes don't undertand. They also are both push by an instinct to the end searching for something.  

Both of the series are similar in terms of ’cave’ exploring and in both series they are trying to find a certain someone While Made in Abyss is a bit serious and fairytail-like, Sakugan is light hearted, funny, and mecha 

Both Sakugan and Gurren Lagann are set into an underground ambiance where most of the humanity live there, using a lot of drilling mechas to advance progress in their worlds. In Gurren Lagann, there's a boy with a young adult who want to become the best of their world. However, in Sakugan, there's a girl with her young dad who only want to explore the world. Shimon and Memempu are very clever children in spite to their young ages, and Kamina and Gagumber are very laid back young adults. 

Similar direction styles and energy 

DECA-DENCE IS SO SIMILAR TO SAKUGAN World with monsters where civilization lives isolated but some of them are "trained" to fight against them outside. Young girls want to combat but the main male characters are scared to let them go because it´s really dangerous. The relationship between both main characters is entertaining and interesting to watch, like "cat and dog" thing. 

- Both had a really strong start and an interesting world but fall flat with boring characters and drama. - Both showcase a daughter and a father kinda relationship.