I don't usually translate lyrics, but I felt particularly inspired by this song and it didn't seem too difficult to do. I did this fairly quickly (15 minutes) so it may or may not be slightly inaccurate, but I trust you'll get the meaning of this song. Feel free to correct me.
Kanji & romaji available here
"Red Bathroom"
Let's make red rain fall
Let's swear "forever" right now
From me to you, as I have feelings of instability
I want you, I want you, I want you
Please look only at me
I'm sorry, I'm sorry
I killed you because I love you
I want you, I want you, I want you
Please accept me
*squish squish squish* Dig it out
With this, you only belong to me, right?
Disconnecting pieces. Does it hurt?
La la la la
I want you to look only at me
I'll decorate the room with your eyeballs
I'll put out your leftover pieces on garbage day
In the bathroom, singing a song, painting it red in a secret ceremony
As you lie there unmoving and covered in red, I copiously pour something white on you
In the dead of night
Why shouldn't I kill people?
Dad and Mom didn't teach me
Even I fell in love with somebody
Though this is the first time I felt this way
If you won't understand, I don't want you
Die die die die
My favourite white shirt got dirty
Let's bury anyone who interrupts us in the garden
With this, we are alone
In the sweet dead of night
That girl looks good too. I want to kill her.
The unending rain, I'll fall in love again
In the red rain, I'm alone again
In the dead of night