“Ours is a forbidden love”. This phrase spoken by Willow about Angel has sparked the imaginations of “unconventional shippers” regarding a pairing between the two since the beginning.
It is not known when Willow and Angel actually meet, but Willow knows about Angel from the beginning when Buffy meets him as ‘cryptic guy’. At the start of their relationship, Willow sees Buffy and Angel meet at the Bronze numerous times but they don’t speak to each other. When Giles, Xander and Willow were trapped in the gas filled room by the Invisible Girl, it is Angel that opens the door for them and carries Willow out to safety. When Angel needs help in looking for information on a boy from Buffy’s past, Angel seeks out Willow for that help. He knocks on Willow’s bedroom window, which suggests that he cared enough to know, not only which house was hers but also which window leads to her room.
Later, Willow becomes comfortable enough in her relationship with Angel to yell at him over his treatment of Buffy. When Buffy sneaks out to go to a frat party and Willow can’t cover for her any more, she feels comfortable enough to yell at Angel “…and you, I mean your going to live forever and you don’t have time for a cup of coffee?”
One of the many ways that showcases Willow’s caring nature and her great capacity for forgiveness is that while still in the hospital recovering from her injuries, Willow works her magic and restores Angel’s soul. Also, after the spell restoration and Angel’s return she is the first of the Slayerettes to forgive Angel for his time as Angelus.
Willow and Angel stay in touch even after he leaves for LA after the mayor’s aborted ascension. Shortly thereafter, Angel returns to Sunnydale for a brief time, because of Doyle’s vision of Buffy in danger. While there, Angel allows Willow to know about him but wants to keep it a secret from Buffy.
When Buffy makes her sacrifice in the battle with the hell goddess, Glorificus, it is Willow that arrives in person in LA to let Angel know of Buffy’s death. This shows the connection between the two still strongly exists.
It is easy to see what Angel would find attractive about Willow besides her looks. She is a very caring person and is non-judgmental regarding the demon inside. Willow’s intelligence would be interesting to explore and she would stubbornly follow you into hell if she thought it would protect you. Willow’s forays into the dark side of magic and her own struggle with her “demon” gives her an insight into what Angel struggles with. Willow sees in Angel a man trying to overcome his past/dark side and trying to do the right thing. He helps in the fight against evil even though he struggles with his demon and he is willing to sacrifice his own happiness by giving up Buffy so that she could move on. Of course he also has the tortured soul bad boy thing going on. ;)
When writing fanfic with Angel and Willow as a pairing, the past relationships shouldn’t be overlooked. It is what made them who they are. Buffy allowed Angel to feel love. Oz and Tara, both gave Willow confidence in herself. Willow’s sexuality doesn’t necessarily have to be an obstacle in the pairing. Her time with Tara shouldn’t be used as an experiment because it belittles what Willow felt for Tara as not real. By the same token, you shouldn’t just say “Gay, now” because it lessens the feelings she had for Xander growing up, her love for Oz and her crush on Giles. Willow is an ‘equalist’, the love she feels is equally distributed between male and female. Buffy as Angel’s soulmate should be dealt with the same way. To ignore it minimizes the influence it had on both Angel and Willow. Willow is Buffy’s best friend and such wouldn’t do anything intentionally that would hurt her.
Since a Willow/Angel pairing would pretty much be AU, a lot of “What ifs” can be utilized. Their time together after the soul restoration in the Buffyverse is filled with “What ifs” that can be used to spark ideas for a story.
What if after restoring Angel’s soul there was a connection? “I think the spell worked. I felt something go through me.”
What if Angel really knew it was Willow nursing him back to health from the arrow and not mistaking her for Buffy?
Angel opens his eyes.
Willow: "You're awake."
Angel reaches for her hand: "You've been watching over me?"
Willow nods. Angel takes her hand and starts kissing it. He lays his other hand on Willow’s right arm.
Willow taken aback and slightly worried: "Well, - we've been taking turns."
Angel: "I thought - I thought I'd never see you again"
Willow looks at him surprised and confused. Angel shakes his head.
"I can't leave you. I was wrong. I need you."
What if the reason Angel wanted to keep his presence a secret from Buffy was because of his feelings for Willow?
What could have happened to Angel and Willow after she told him about Buffy’s sacrifice?
How would Angel help Willow deal with the consequences of walking on the dark side of magic?
There are a lot of good stories out there that pair Angel and Willow. Learn from what others have written and explore new and different ways to take their relationship whether as friendship or a romantic pairing. A pairing between The Dark Brooding Tortured Soul and the Perky Pixie and/or Bad Ass Wicca is loaded with possibilities and a lot of different paths not taken. Have fun exploring them all.