Your first kiss wasn't with Mana!You haven't, have you?Makoto..... Have you kissed Mana yet?It was with me, Hishikawa!The means don't matter! If kissing works, then that's fine! Now Mana and this girl will be through! Even if she sees Mana, she'll just feel yuri embarrassed!
The crossed out Japanese word is キマシ (kimashi). This is short for キマシタワー (kimashita wa-), which is a saying used when there are depictions or suggestions of lesbian feelings or yuri in an anime, manga, or the like.
The phrase originates from Strawberry Panic. In episode 11, Suzumi Tamao is waiting in a thicket to surprise Aoi Nagisa (the girl she is obsessed with) during a test of courage. As Nagisa approaches, Suzumi says the phrase. More fully, what she says is "来ましたわ (kimashita wa)。驚く渚砂ちゃんはいったいどんな声で泣くのでしょう。楽しみですわ~。" ("Here she comes. I wonder what kind of voice she'll cry out with when she's surprised. I'm looking forward to it.")
At some point, someone created ASCII art of the phrase along with Suzumi's face. While the anime was airing, 2channers used the ASCII art and the phrase whenever scenes suggesting yuri came up.
Original scene from Strawberry PanicNicoPedia entryMomokami entryMakoto... After this I'll comfort you, davii...That is, in my own way...