I Pilot a Mecha in One Piece

The early chapters focus on building up strength!

Kane transmigrated, but unlike most people, he didn't start with a bowl. He found himself inside a giant iron cage.

Just as Kane was despairing and ready to accept his fate, the System arrived. But he couldn't bring himself to celebrate, because this lousy System was always trying to kill him!

Multiple female love interests, slow-paced, not a power fantasy. Read with caution!