The defender joined the Club last summer but sadly, suffered an ACL injury just three months into her new chapter.
With a well-taken penalty in our Champions League triumph at Lugano, the 24-year-old wrote her name onto the scoresheet for her new Club - but that fine finish is not her favourite City goal...
In the latest of our feature, presented by Nissan, Mannion shares her most enjoyed City strike...
My favourite goal was Lauren Hemp’s winner against Arsenal.
It was a really pivotal goal and it was just so well-created with the set-up out wide from Keira Walsh and the header from Hempo.
We were at home, there was a brilliant crowd and it was such a crucial win. Everything about it was special.
CITYZENS AT HOME | Fun & educational activities to do at home
We always have breakfast together and sometimes, you get a feel for the vibe.
Although I haven't been at the Club long, I've noticed there's always an expectation to put in a good performance to win the game.
At other clubs, I think some players hope to have a good feeling or hope things will fall kindly. At City, you expect to perform well and even if you're having a difficult game, you know there are players on the pitch who can pull something out of nothing.
If they can do that on a bad day, imagine what it's like on a good day!
We're always confident. The players put the work in everyday so matchday is almost the treat at the end of the week.
The culture is to train as hard as you play.
WE'RE NOT REALLY HERE | Shop the range
Watching from the sidelines
It was hard at the start. You can feel quite detached but as time has gone on, it's been a joy.
For me, it's been the next best thing to playing and I've been soaking it in - the atmosphere, the joy of watching women's sport.
When you're in the midst, playing, the whole day is about you: 'How am I preparing? What is my role in the team? What does that mean for me? Am I taking enough liquids on board at half-time?' Those little details...
When you're not actively part of it, you sit back and watch, and think: 'Wasn't that amazing? Wasn't that good?'
It's been a nice switch, refreshing... and you're still part of something. You're wearing the kit and the badge, representing the Club as an ambassador.
You can help to build your teammates up and I've loved that - seeing the girls do good things and telling them.
When you're playing, you don't always think about being encouraging or complimentary. The players don't need me to tell them when they're doing something good but it's nice to be nice!
CITY+ | Premium City content
It was such a huge game and also Nick Cushing's final game in charge. We had to win.
I was sat with the fans and the attendance was amazing. There was such a good atmosphere. I took a picture of the big screen when the attendance was announced.
When you're playing, you can't take a breather, look around and think: 'It's amazing how many people are here!'
It was a lovely moment. The team were winning and I remember thinking: 'Look how far women's football has come!'
It was such a great header and nothing more than Hempo deserved.
She's been our real breakout player for both City and England. When you're young, those moments can really define some momentum, especially as a forward player.
You play off those moments - they spur you on to more goals and good performances.
Long may it continue.
It wasn't a bad delivery! It's annoyingly effortless for Keira!
A few weeks earlier, she scored an outrageous goal with a first-time finish at Birmingham.
There isn't a goal that resembles City any more than Hempo's goal against Arsenal: Keira Walsh - a City fan from the start - with an amazing set-up and assist to Hempo - our breakout player - who puts it in the net to win the game.
That's everything City in a nutshell!