Ghost Blade HD (HP)

You start the game with three Continues, but you can unlock up to nine, which is when the trophy will pop. Unfortunately, the exact requirements are obscure and after testing a few things I couldn’t find a definite answer. Most players unlock more Continues as they Continue and fail on Normal and Hard runs and also on Score Attack (which is where I unlocked the trophy). It seems that blindly suiciding and consuming Continues on purpose won’t unlock more so my guess is that they either unlock after accumulating enough playtime or the game wants you to actively play a part in unlocking them, such as reaching a certain score, combo or killing enough enemies before dying and using all Continues.

All things considered, the most foolproof way to unlock more Continues is to keep on playing all modes “normally” and use all Continues at disposal without suiciding or playing poorly on purpose.