Japanese by Example
Learning through examples in manga

Furthermore, it's just a bonus item with それに〜

Grammar Explanation: In addition to with それに〜

ストロボ・エッジ » Volume 1 » Page 23

Ninako is on the train after school when she notices Ren, a popular boy from school, sleeping a few seats down. The boy suddenly wakes as the train comes to a stop, and he hurries to get off, accidentally knocking Ninako’s phone from her hand. It falls to the floor, and the phone strap charm breaks. Ren misses his exit as he stops to apologize to Ninako, saying he’ll replace the charm.

仁奈子(になこ):
「だっ　大丈夫(だいじょうぶ)ですっ」
"I---it's all right."
「ケータイは無事(ぶじ)だし！」
"Since my cell phone is safe!"
「それにこのストラップただのジュースのおまけだし」
"Furthermore, this strap is just a juice prize."
「しかももうだいぶ前〜〜〜〜のやつで古いから」
"Plus, it's from way back when, so it's old."