How do i level up other chracters on my team quickly?

Soloyolio

So just yesterday i got Momo Hinamori and saw that she was level 30 so i leveled her up to level  44 and am now stuk there, i was wondering if there is a easy way to level her up since i dont have any exp books left.

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what is your level?
and if you feel like it you can use her in your formation for pve event

and on a side note your other characters level cant surpass your main lvl

Soloyolio

I am level 55

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then mayb you should use her in your pve event daily and have her on your formation when claiming reward that have exp in the attachment.
other then that there is the exp scroll only this 2 method are avail for us actually