Why don’t we open his memorial concert with everyone?
Follow people who grieve by mourning with them. You don't want to be the only one who doesn't seem sad.
This is a jukugo word that uses the on'yomi readings of the kanji. You didn't learn this reading for 追 yet, so here's a mnemonic to help you:
You're mourning the loss of your pet pig. You can't help but yell SOOEY (つい) to the sky, hoping she'll come back to life. It doesn't work so you stay in a state of mourning for the rest of your life. She was your best pig friend, after all.