I read a bit of this one and now I can't remember what it was called. She literally bumps into him and yells at him. All the people around her thinks she is crazy and then in another part, Sesshoumaru goes into the subway and talked to a large demon and learns that there is a threat to his territory. Please help it you know this.

This story sounds very familiar...was it on spark, before it merged with dokuga? if so i think i know what you're talking about about...i wont make any guesses yet...until i know if it was on spark/fanfiction/dokuga/AFF...

Did she bump into him on the train, and then realised who it was, and got worried he'd kill her. I remember something like it, but can't remember the name,but it was on spark, but there was only one chp.

Kagome bumped into him in the street and I don't think that it was on spark, there were only a couple of chapters. Sesshoumaru is not visible to anyone else. He was dress just like in the feudal era I think and Kagome was wonder why nobody was looking at him.

The second chapter was on his visit to the demon in the subway. Sesshoumaru thought about how the world had changed and the separation of the demon world from the human world.

If I think of anything else I will note it.

gah! I can't sleep...so I came on here. tis bad cus i have to be up in 3 hrs...Yay for 4 am -gags-
anyway, i did a quick search and I when I looked up the demon in the subway part, I did get a couple results but I doubt they're what you're looking for. both are on fanfiction.net

The first is Faded Memories by Chiera
Faded Memories » reviews
After a very tragic event occurs, Kagome's is sealed, causing her to forget all about her travels in the past. She lives in her own time now, and everything's going just fine. Until she meets a familiar face. - Sesskag - Written in 2006 - Edited in 2009
Inuyasha - Rated: M - English - Drama/Romance - Chapters: 27 - Words: 109,414 - Reviews: 510 - Updated: 6-27-06 - Published: 1-1-06 - Kagome & Sesshomaru - Complete

then theres this one:
Concordia Discors by Enkida » reviews
On a seemingly normal trip back to the modern era, Kagome suddenly realizes the consequences of playing with the past. In trying to discover a balance between two vastly different worlds, she finds help from the most unlikely of sources. COMPLETE
Inuyasha - Rated: T - English - Drama/General - Chapters: 11 - Words: 60,875 - Reviews: 129 - Updated: 3-27-06 - Published: 3-3-06 - Kagome & Sesshomaru - Complete

Do either sound familiar? I haven't read em, just skimmed em, so I don't know if they're any good...

No, both are not the story. I wish I had bookmarked it. But it was only a few chapters and I usually wait until there are more before I mark them. I will keep looking, but it may have been removed by the author.