Full Metal Panic! The Second Raid

They both have a secret organization trying to intervene in war. They also both have characters from the Middle East that were war children. 

Extremely dense male lead and a strong female lead who tries to convey their feeling to their respective male leads...o yea both have to do with fighting as well 

Both are predominantly military animes with some comedy and focuses on an independent organization. Both have fights against terrorists and both have an agressive girl as protagonist. 

Code Geass and FMP are similar because of the "mecha" theme. Code Geass is actually fighting using those "robots" like the one in FMP. You should give them both a try. 

Both involve organizations that unaffiliated with any nationality. Both male leads are underage soldiers. Also, guns, guns, and more guns!!! 

Both shows detail the life and transition of a mercenary to a high school student. While Full Metal Panic! has more of a comedic undertone, both shows have a decent amount of action, violence and blood. Grisaia takes more of a harem/romance path, both shows are quite similar in regards to the MC. If you liked Full Metal Panic! Grisaia will not disappoint you; it takes much more of the mature and darker route that Full Metal Panic! did not quite touch on. 

Both sequel that elevate their franchise to a higher status. Both are also adapted by KyoAni and focuses on the main characters and their struggles during the entire show. 

Both feature heavy action with the use of tactics, great character development, and believable character interactions. 

Both shows focus on military action in a fictional version of modern China. Both Canaan and FMP! The Second Raid feature teenagers being used as expert soldiers or highly skilled assassins, trying to deal with the traumatizing experience on the battlefield. In both shows, the main character has a civilian friend character who helps him/her relax between the missions. As for character archetypes, the teenage soldier protagonists of both shows face yuri twins as cruel villains in both storylines. Regarding the action sequences, an enormous body count and an excessive use of 3d model helicopters or other military equipment feel especially striking. Contentwise, both shows express a very similar pseudo-nihilistic philosophy and atmosphere. read more 

Chidori really reminds me of Ayano. The thing is that Chidori is WAY more likeable than Ayano! 

Mecha wars with a romantic backstory. 

Harder, better, faster, stronger. As their titles say, they are grittier 2nd seasons of two fantastic series, enhanced with solid animation, lots of action, various amounts of violence and drama, and many crazy characters, including two of the most badass women ever seen (Revy & Melissa, yes indeed). Both series also involve, in their background story, an extremely tragic and intimate bond between two twins who are as pretty as they are lethal (Hansel & Gretel/Yu Lan & Yu Fan). If you liked FMP but want something darker, check Black Lagoon out; if you're a Black Lagoon fan but also enjoy mecha series, try FMP. 

Both have similarity on character development, especially between the main characters. Both are mecha anime. Moreover, both of their mecha can interact with main characters and providing same reason for their fighting.... Protect the Love one.