I Can Accumulate Proficiency, Starting from Alchemy - Chapter 497 - 252: Jade Arm Memories, Great

Yun Bixue is in dire straits—

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

One morning, after being bound to the system, MC started his routine of always being captured/ attacked by the ML.

It doesn’t matter if he transmigrated into the ML’s little brother (TN: Here I think brother disciple) or master or opponent, but in the end he is still forcibly taken by the ML.

After transmigrating to many worlds:

MC: Come out system!!! The heck?! Why do these MLs not love their female goddesses, but insist on doing it with me! Aaaaahh!!!

System: …. __(:3」∠)_ Don’t ask me, I also don’t know.

- Description from Novelupdates

Everyone has a system they just need to meet hidden conditions to unlock it. A blacksmith system may unlock after a human walks by a forge. A master mage may unlock a system after attempting to control the mana in their body. Even something as simple as kicking a rock at a bucket can unlock the marksman system a unique system allowing for perfect accuracy. But what happens when someone reaches the age of fifteen and hasn’t unlocked their system? Walker is about to find out, time is ticking and he doesn’t want to live out his life as an ordinary human; he has dreams you know!