April 23, 2018 - Kitagawa Ryo and Hashimoto Momoko leave Hello Pro Kenshuusei
On April 23, the official Hello! Project website updated the list of members participating in the upcoming Hello! Project Kenshuusei Happyoukai 2018 ~Haru no Koukai Jitsuryoku Shindan Test~ event on May 6, and it was noted that both Kitagawa Ryo and Hashimoto Momoko had ended their training and therefore would not be participating in the event, or any future Hello! Project-related activities.
Kitagawa was a first generation member of Hello Pro Kenshuusei Hokkaido, a regional branch of the main trainee group, having joined on July 31, 2016 following the Hello! Project "Hokkaido Gentei" Member Audition. During her time in the group, she participated in two singles: "Real☆Little☆Girl / Kanojo ni Naritai!!!" and "Hankouki! / Ice day Party", whereas Hashimoto was a newer addition to Hello Pro Kenshuusei, having joined as a 28th generation member on December 10, 2017 following the Hello! Project Shin Member Audition.
Source: Hello! Project

April 5, 2018 - Wada Ayaka to graduate from ANGERME and Hello! Project in spring 2019
On April 5, Wada Ayaka, the current leader of ANGERME and Hello! Project, announced on her blog that she would graduate one year from now at the end of ANGERME's 2019 spring tour.
Wada has discussed graduating since last year, and this year she became set on the decision. She wants to continue working as an idol after she graduates and express herself through not only singing and dancing, but in various other ways.
Source: Hello! Project, Wada Ayaka Official Blog Entry

March 30, 2018 - Update on Ichioka Reina's new group, and Takase Kurumi and Kiyono Momohime's new section
It was originally announced on May 5, 2017 that Hello Pro Kenshuusei members Takase Kurumi and Kiyono Momohime would specifically debut in a new theater-focused section while Ichioka Reina, Danbara Ruru, and Kawamura Ayano would debut in Hello! Project. On June 26, 2017, Kawamura became a member of ANGERME and Danbara became a member of Juice=Juice, but it was announced that Ichioka would instead become the leader of a new group. Until now, this was the last news fans had heard.
On March 30, 2018, an update on the status of their group and section was posted on the official Hello! Project website. Ichioka Reina will lead a "performance group" that aims to elevate singing and dancing through physical expression. Takase Kurumi and Kiyono Momohime will form a group with the image of a "small theater troupe" that uses expressive power and theatrical elements in their singing and dancing.
An audition for new members to join either of the two groups will open in late April. Members may also be selected from Hello Pro Kenshuusei. Both groups are expected to begin independent and joint activities between the summer and fall.
Source: Hello! Project, Hello! Project (Audition Announcement)

March 27, 2018 - Ogata Haruna to graduate from Morning Musume '18 and Hello! Project
On March 27, it was suddenly announced that 12th generation member Ogata Haruna has decided to graduate from Morning Musume '18 and Hello! Project on June 20 in the Morning Musume Tanjou 20 Shuunen Kinen Concert Tour 2018 Haru ~We are MORNING MUSUME~ finale at Nippon Budokan.
For the past year, she has been studying for entrance exams while working. She was recently accepted into a junior college, which she will begin attending in April. However, she will face the difficulty of balancing idol activities and college due her having lectures every weekday from morning to evening. As she also plans to transfer to a four-year university afterwards, she has made the decision to graduate from Morning Musume to focus on her studies.
Source: Hello! Project, Morning Musume 12ki Official Blog (Ogata Entry)