*your eyes whispered have we met*

XL/FFB has switched identity but the FL still recognises and thinks it's him for a short while until proven otherwise. XL/FFB acts completely different and pretends that she has mistaken him for some else. FL still comes to gradually realise that the XL/FFB is the one and only because of clues he's shown her.

After the FL reverts to her true identity, she pretends to have no memory of the ML, but he refuses to believe it and is desperate to recover her memory and restart their love. 

To keep it simple, ML thought FL was dead. They're both under a new identity, with the FL resuming her true identity, when they meet again and the ML immediately recognises her, but she is quick to deny it. ML doesn't believe her.

While everyone believes FL is dead, ML still has hope that she is alive. FL comes back but under a new identity. ML is convinced she is her and continually tests her even when she denies it. I love how when she came back (under a new identity), he made sure to keep her close to him because of how much he misses her. 

While everyone believes the FL died, she accidentally comes back into the ML's life again under a new identity but with no recollection of her past life. But because the FL shows hints of old habits, the ML keeps her close because he suspects that it might be her.

ML pretends to have amnesia but the FL knows better and he is shortly outed because of obvious clues. 

ML pretends to have amnesia but uses this chance to kiss and "fall in love at first sight" with the FL.

ML pretends to have amnesia, hurting the FL's feelings even though it pains him to do so because of reasons. 

ML has changed identity but the FL is convinced he is one and the same and tests him. ML has to keep pretending even though it also pains him.

ML pretends to forget about the FL, hurting her, and in turn hurting himself.

FL forgot about her past with the ML, but ML still remembers. But when they meet agin, he acts like it's also the first time he met her. 

They both pretend not to have known each other before.

They both transmigrate to historical times. The love interest pretends to not know the ML for fun. 

FL is presumed to be missing/dead but ML still has hope. FL comes back into his life but with amnesia and under a new identity. ML is convinced she is her.

ML saved FL years ago but because he was wearing a mask, she didn't know what he looked like. When they meet again, ML recognises her but pretends they've never met before. 

ML recognises the FL but pretends they've never met.

FL and ML met when they were children and during that time, he developed a crush on her. Years later, they meet again and he recognises her but doesn't mention their shared history.

FL and ML shares a tragic past but because the FL developed amnesia because of it, only he remembers her.

FL pretends to get amnesia.

ML and FL used to be in a relationship but because of some incident, she pretends to get amnesia, forgetting him. 

ML and FL used to be in a relationship but he somehow gets amnesia. She comes back into his life again but denies that they previously knew each other when he gets suspicious of why she knows so much about him.

FL pretends to have amnesia, forgetting about her history with the ML.