Legal remedy against false rape allegation & obscenity case

My friend's Lover logged FIR against him saying he raped her in sept-12 and continued raped till dec-16, case launched in Oct-2017, with section IPC 376,506 & IT section 67. he was arrested & released on regular bail withing 15 days. He was in physical relation with her since last four year with consent of each other. but in sept-17 she wanted to go away from him. Both are married aged 36 and 44. he requested on text message not to go away, but she did not agree. he message her so many in tense mood requestive type & also threatened for her nude photo will show to her husband which she herself shared him on whatsapp. Both were really good friends and were chatting daily on whatsapp. all conversation of whats app deleted. my freiends mobile is ceased by police and found her nude photos which were shared by lady friend on his whats app.actually my friend has not shared these photo to any social media stie or any other media. please guide how he can be defend and release from this case.