If you use other rares with abilities to train another idol, there's a chance for the buffed idol to get an increase her skill level-
How does the skill level affect the skill, and what's the cap for it?
I'm curious about it too. I played for a couple of years without ever feeding upong a Rare, because Rares were so few. They could only be gotten with paid-for gacha or by claiming a stage bonus. So, it never tried that. But when they opened the bonus floodgates three weeks ago, there was a whole bunch of very old unclaimed rares from a year ago, who come with heart max of zero. I basically had no use for them, save to feed them to my newly-acquired S-rares. Lo and behold, a couple of those were levelled up (with the blue "LevelUp" message -- it's the first time I saw it ever).
Here's what the wiki says:
"
Special Ability (rare and up only): rare cards have special effects. They can boost a certain type or all idols' stats and/or reduce the opponents' stats. There's a 40% chance to increase the effect's effectiveness when you "feed" an other rare card to it, using lesson."
What "certain types" it's talking about is the question.
