Hunter X Hunter

Gon, Leorio and Kurapika stay in the Zoldyck family's servants' quarters at the security guards behest. Zebro lets them in through the Testing Gate (weighing tons), and Gon feels he should have been able to let himself in. While they stay there, the guard trains them with weighted brooms, water buckets, slippers, cups and whatnot. They end up extremely strong. After 20 days they are able to open the gate themselves, and they start walking through the grounds towards the house. Gon and Kurapika can push the first gate of 2 tons open, and Leorio is strong enough for the second gate.