this year valentines event will feature very few servants and I did voting a while back on who should be included in this but I didn't get any comments on it so this is just me making things up.

Izami pieces (demonic valentine: shiva)

Personality: izami once again claims a spot on another event, this version of izami has been drawn into a separate world along with the main character and the rest of 7 lovers. She is still izami though nothing has really changed about her
Event ability: demonic valentines: shiva (it's the same ability that she always has had except this time it's Valentine's Day themed, double power during the month of February)
Hidden abilities: pink ice
Partners in crime
Weapons: none
Grand magic: dance of the black roses
Characteristics: grand summon, female, magician, Valentine's 2020,
Rank: EX
Class: caster
Rank explanation: izami's Valentine's Day form is basically the same as her Halloween event version so their good for the same reasons despite both being casters, I would say that this version is slightly better thanks to a better grand magic.

Kirami skulls (harmonic valentines: raja)

Personality: for some reason kirami was made into an Angel after she was drawn into the separate world but that's all that's different about her.
Event ability: harmonic valentines: raja (again it's the same old thing but Valentine's Day themed, she has double power in the month of February)
Hidden abilities: perfect harmony
Devils brand (thunder) (doubles the power of all electric magic but when she fights she slowly loses her life force)
Weapons: harmonic sword
Class: warrior-caster
Grand magic: dance of the pink peonys
Rank: A
Characteristics: grand summon, female, magician, Valentine's 2020
Rank explanation: kirami doesn't do a whole lot to separate herself from the other warrior or caster servants and since she doesn't specialize in either class she falls short in both. Her event ability is good but we already know that so let's look at her hidden abilities. Perfect harmony is a good ability, it's the same one that's on her naughty or nice version and it lets her at the very least match any opponent but devils brand (thunder) kind of lets her down because it puts her on a timer which isn't good seeing as how she doesn't have a lot of ways to boost her fire power any further

Sophia von sweet (maid sweets)

Personality: Sophia has been brought into this separate world and she became a maid.... for no real reason.
Event ability: maid sweets (her protection magic is doubled in power, she has double power in February)
Hidden abilities: protective love (she takes half damage from all caster and warrior class servants)
The best offense (she can use her protection magic to attack her opponent in less conventional ways, she can cast spells much faster than the average caster, up to 10 times as fast)
Class: warrior-caster
Grand magic: dance of the bluebells
Rank: EX
Weapons: sweet saber
Characteristics: female, magician, Valentine's 2020
Rank explanation: Sophia is a very straight forward servant, she isn't going to die very easily and she can dish out reliable damage, her grand magic is a damaging grand magic which helps her cover up herself low damage numbers. Offense however is now what she specializes in, Sophia is similar to ereshkigal in that they can both outlast opponents far stronger than them thanks to their hidden abilities and because of that they can beat a lot of the other servants in their class hence why Sophia is rank EX when her abilities on their own in a vacuum are more B tier.

Noah strike (Egyptian gold)

Personality: Noah's pretty mad about his hair getting cut as they entered the separate world but that's it.
Event ability: Egyptian gold (his power grows the more money he and his master have, double power in February)
Hidden abilities: golden sands (he gains double power in the desert, he can create a desert reality marble)
Golden age (body) (he can regenerate passively)
Weapons: sword of the Egyptian lily
Grand magic: dance of the white lilies
Class: warrior
Characteristics: male, Valentine's 2020, magician, Egyptian
Rank: A
Rank explanation: Noah is a warrior class servant who just doesn't have the same power as his fellow warriors.  He loses out because his hidden abilities don't have a lot of effects and the ones they do have are good but not that great, he's got a basic damaging grand magic with no bonus effects so he doesn't even recover in that area.

Aster shards (the lovers)

Personality: aster has been brought into this separate world and infused with the lovers arcana so you can imagine the effect it had on him
Event abilities: the lovers (he can charm male and female opponents with his attacks, double power during the month of February)
Hidden abilities: arcana fever (lovers) (he gains double power whenever he is in love or someone else is in love with him)
Heartbreaker (deals double damage to those in love with him, deals double damage to those he has charmed)
Grand magic: dance of the red roses
Weapons: none
Class: caster
Characteristics: male, American, Valentine's 2020, magician
Rank: A
Rank explanation: aster has the best charm based niche amongst casters, Nero's valentines form from last year comes in second place because he can more reliably inflict charm but aster can actually do a lot of damage against charmed enemies due to his abilities.  His grand magic let's him down though because on one hand it's a guaranteed charm but it loses out on bonus damage if the opponent isn't charmed.

Arthur Sinclair (color-bursting with love)

Personality: Arthur was dragged into this alternate world while watching his brother, Peter, duke it out with Mirato striker and somehow he's picked up some of peter's tricks
Event ability: color-bursting with love (he gains the effects of the hidden ability "the power of imagination" ((the power of imagination allows its holder to create solid images out of pure liquid magic that they can excrete from themselves, with enough concentration they can even form whole human beings or reality marbles)) double power during the month of February)
Hidden ability: poisoned soul
Tainted heart (he can take the sins of others onto himself and the more sins he takes onto himself the more powerful becomes and the more sanity he loses
Class: berserker
Characteristics: male, saint, Valentine's 2020, magician, American
Rank: A
Weapons: ornate katana
Grand magic: dance of the white roses
Rank explanation: Arthur is not a servant who's going to stick around very long, he has 2 abilities which make him more powerful but lower his usefulness in long term battles, poisoned soul directly eats away at his life force while tainted heart chips away at his sanity. His grand magic allows him to purify himself of his sins and reset his sanity but by doing this he reduces his threat level

Mata Hari (valentines mistress)

Personality: she appears to be the only servant affected by this strange new world, she is a strange servant who never appeared before this event. She calls herself Mata Hari and acts a bit like her but all in all she seems like a completely different person.
Event ability: valentines mistress (double power during February, double power against male opponents)
Hidden abilities: devils brand
Heartbreaker
Class: caster
Weapons: none
Characteristics: female, French, non-magician, valentines 2020
Grand magic: dance of the 7 flowers
Rank: B
Rank explanation: she doesn't have a charm niche but has an ability that works great with charm (heartbreaker), but her lack of a charm makes that ability almost useless. She has a bit of an anti-male niche but a lot of other servants also have that same niche and they do a better job with it, her grand magic deals a small amount of damage and seriously debuffs her opponents but that only evens the scales a little bit

Peter Colorburst (joyous spring)

Personality: Peter has even brought into this separate world along with his boyfriend as a moderator of sorts, he's kinda confused and doesn't really Care about the whole things since he'd rather be spending time with Simon
Event ability: joyous spring (can preform a joint grand magic with anyone who has the ability "tragic fall", deals double Damage while fighting alongside someone who has the ability "tragic fall", double power during the month of February
Hidden abilities: the power of imagination
Partners in crime
Class: assassin
Weapons: painters knives
Grand magic: a painting of a joyous spring
Joint grand magic: joyous spring and tragic fall!!!
Characteristics: male, magician, American, valentines 2020
Rank: EX
Rank explanation: Peter isn't that great on his own since he doesn't have any abilities that really enhance his performance as an assassin but when working alongside his partner servant like he's supposed to he becomes a major power house and both his grand Magics can deal an immense amount of damage.

Simon hounds (tragic fall)

Personality: Simon has been brought into this separate world along with peter to be a moderator of sorts, he doesn't really care because he's too focused on Peter
Event ability: tragic fall (it's the same as joyous spring but in revere)
Hidden abilities: partners in crime
Hangman's trick (he can create illusions and reality marbles on the spot, mana cost for illusion magic is halved, success fate of hypnotism magic is doubled)
Class: ruler
Weapons: pocket watch on a chain, silver dollar
Grand magic: the illusion of a tragic fall
Joint grand magic: joyous spring and tragic fall!!!
Characteristics: male, American, magician, Valentine's 2020
Rank: EX
Rank explanation: Simon is good for a lot of the same reasons that peter is good, on his own he's still a serviceable servant but definitely not the best in class let alone overall, but when he's paired with peter their strength is undeniable. Simons ability to create reality marbles and distract the opponent works perfectly for the slower assassin approach that peter takes and the power of imagination allows peter to protect Simon from being destroyed by stronger opponents by giving them something else to focus on. His grand magic does a small amount of damage and buffs him up by a lot but it's nothing compared to the immense damage his joint grand magic can do