Wait.... since she has higher base stats, wouldn't she eventually surpass our mc...
...is what I originally thought. I did the maths, and
assuming leveling up gives a flat increase to stats (I wouldn't think so but I'm going off on what we currently have), our mc still has her beat even if she has high base stats.
I will assume that our mc is a normal person summoned to another world, and has not gone through some crazy training like our heroines. So, going off the information of the level 1 farmer in ch4.2, I'll have our hero have his HP, ATT and DEF all start at 50 (MP doesn't change/isn't taken into account since we see that Abeno's MP doesn't go up even when she leveled up) to give him a slight headstart over our average farmer.
(Stats are taken from ch4.2 and ch4.4 respectively)
Taking his assumed lvl1 HP of 50 taken from his lvl78 HP of 6455, we are left with 6405. Dividing that by 77 (the times he has leveled up) we have 83 HP per level up when rounded down. Using the same calculations on Abeno, she gains 50 HP per level up (rounded up).
I did this with his other 2 stats (His magic stat isn't shown so we discard that), and comparing it with Abeno we have stats gained per level up:
{Daiki/Abeno}
HP: 83/50
ATT: 60/42
DEF: 41/31
Granted, his stats may have been boosted by external factors and gear, but seeing how he displayed it while in school uniform and stating that those were his stats there and then, I'll assume gear isn't taken into account.
Take this information with a grain of salt as we are assuming leveling up only adds a flat amount of stats, and is not exponential or multiplicative in any way.
Edit: I didn't read the older comments before posting this so I didn't see
@kp114330 comment regarding level up stats. Sorry about that mate.