How to get in contact with Furudate Haruichi?

Furudate Haruichi is a manga artist currently employed by Shueisha Inc.
His/her (the author's gender isn't known) manga Haikyuu!! is serialized in Weekly Shōnen Jump published by Shueisha and I would really love to send him/her my fan mail.
I know that I have to send it to the company's adress Shueisha. But that's all I know!

To Shueisha Inc.
(I know I have to write something here...maybe Weekly Shōnen Jump?)
Furudate Haruichi
Tokyo 101-8050, JAPAN

Could you be so kind to help me? I can't buy Furudate Haruichi manga since in Portugal manga is really rare to find and the editors don't really care about is anyway so I can't see the adress they give for cases like this. He/she is my favourite mangaka! Please help!

You send it to the editorial department of Shonen Jump afaik

〒101-8050
東京都千代田区一ツ橋2-5-10
週刊少年ジャンプ編集部
古館春一先生

Japan
1018050 Tokyo, Chiyoda-ku
2-5-10 Hitotsubashi
Weekly Shonen Jump Editorial Department
To Furudate Haruichi

Mr. Furudate Haruichi
c/o Weekly Shonen Jump Editorial Department
Shueisha Inc.
2-5-10 Hitotsubashi
Chiyoda-ku, Tokyo 101-8050
JAPAN

...is the correct way to write it.

Shonen Jump also seems to have an English agent that says they will forward fan letters to manga creators.
http://www.shonenjump.com/j/index.html
https://www.viz.com/company-faq#0_9

Thank you so much! Both of you were really helpful :)
If there's something I can do in return just say it.