Young boy is a super genius with a secret underground lab where he builds futuristic tech. Has a harem with the next door sisters. Robotic spiders? I believe he also helps rescue distressed/trafficked girls.
Young boy is a super genius with a secret underground lab where he builds futuristic tech. Has a harem with the next door sisters. Robotic spiders? I believe he also helps rescue distressed/trafficked girls.
Probably not the requested ones, but partially fits if you knock some corners off and use a big hammer: Kenn Ghannon's Pretty CAPable and Fairly CAPable (swarm stories).
Young boy -ish
super genius -yep
secret underground lab -yep
builds futuristic tech -yep
Has a harem -eventually
with the next door sisters -nope BUT does take a pair of shirt-tail relative sisters
Robotic spiders -no
helps rescue distressed/trafficked girls -yes, ish.
The only thing I've seen on SOL that would remotely fit is what madnige mentioned.
That said, it almost sounds like Dexter from Dexter's Laboratory aged up to high school years.
https://en.wikipedia.org/wiki/Dexter%27s_Laboratory
I believe you are referring to Boy In The Grass by Magusfang. It's not on this site.
I'm pretty sure this isn't the story line you're thinking of, but the description reminds me a bit of the John the Genius series by PT Brainum