Where can I check the 'Teach Me Quest' strength level 125?

On the other hand, the ludus side doesn't have a 'strength' stat. Do you know any event details?

Did this go over?

On an individual level, the HP is showing numbers that exceed the limit...

The heart (and sword and staff) at the top left is the 'Fighting Spirit' stat. It increases character abilities (making them stronger), but... is this what you're referring to? ^^

There was a similar explanation during a previous event... (though that explanation was also a bit vague)