For any completionist out there. I tried to get all LV.M with a minimal amount of cheat, and just want to share my understanding here. Please feel free to correct me if I am wrong or provide any additional information.
Clothes (Top left): Just buy all the clothes and get the unlock the pregnancy status to unlock LV.M
Sex (Top): Get to 15000 sex (creampie) experience or higher. Can do it by yourself or NTR.
Work (Top right): (Not 100% sure) I believe that is assoiated with the amount/experience from working. LV.12 is LV.M.
Base (Left): Base Level. Get to LV.M from story progression.
Battle (Middle): Battle Level. Get to LV.M after finishing the final boss.
Game (Right): Get to LV.M by completing all games with LV.M.
EP (Bottom Left): That's the EP experience. You will be most likely get to LV.M from grinding something else.
Trophy (Bottom): (Not 100% sure) Getting the stats to certain milestone will increase this level. LV.10 is LV.M.
1 Monster Kill. Just grind.
2 Deaths. Not game over, just returning to base. Grind as well.
3 (Not 100% sure) I guess is box opened. The maximum I can get is 2XX boxes (looking at save data). So not sure if 355 avchiveable but maybe this is item obtained, which can be farmed in the EP fragment arena area.
4 GP Earned. Grind actively or passively.
5 (Not 100% sure) From the number I get legitmately, I guess this could be item collected by walking, like the cherries and crabs. But that is just my guess.
Hope this helps.