Achilles

Achilles is a supporting character in the Reader-Insert, Jealous, and acts as one of The Reader's crew of Servants and main love interests.

Background
I am not writing this whole thing out, thank-you-very-much. What I will mention, however, is that The Reader has had Achilles ever since Da Vinci expanded the reach of the Summoning Chamber, and is one of their more recent Servants.

Appearance
Achilles is a tall young man with a face that is easy on the eyes. He has light green hair with a tuft hanging over his left forehead and golden eyes, almost always smiling.

Personality
Achilles is a very carefree and easygoing individual, only doing what he feels like doing (though he takes his Master's input into consideration as he does) and is the type to both search for adventure and attract danger. He's also a bit cocky and very confident, though it isn't ungrounded as he could easily beat some of the strongest Marines or Pirates in the entirety of the One Piece world.

He acknowledges that this would make the journey boring for Luffy and thusly tends to hold back. However he can forget to tone it down a bit when he sees The Reader or another close one hurt, such as during the encounter in Enies Lobby when The Reader was badly injured while he was trying to reserve his Magic, Achilles force-manifesting so he could give the soldiers who hurt his Master living hell. He went as far as to take from his own Mana reserves to not put strain on The Reader and carried them to safety.

With his feelings for The Reader (which he initially tries to brush off as passionate desires to protect them), Achilles is strangely shy - odd, taking his flirtatious and confident attitude into account. However he has his moments of bravery in which he outright does something bold that has heavy implications of his affections. Achilles is the first to truly realize and somewhat act upon his feelings.

The Reader
Despite being one of their more recent Servants, The Reader is very fond of Achilles, resulting in a close bond and Achilles' eventual infatuation. Achilles is also the only Servant they have spent enough Holy Grails on to get him to Level 100. Achilles makes The Reader aware very early on that he has feelings for them and therefore wants to attempt to pursue a relationship with them, but acknowledges that The Reader doesn't seem to reciprocate these gestures and is willing to wait however long it takes to gain their affections.

This makes their relations a little awkward, but more trusting and ultimately stronger as The Reader feels they can trust him more, which makes Achilles very glad as he likes it when The Reader relies on him.